in this article:
As reported on the World Health Organization (WHO) website, flu is caused by a viral infection that spreads easily among people, circulates all over the world and can affect people of all ages. The climatic differences mean that in the temperate regions the virus circulates with greater intensity in the winter months while, in the tropical regions, it is present all year round.
Globally, every year, flu virus affects between 5 and 10% of the adult population, an incidence that rises to 20-30% in children. Between 3 and 5 million cases of influenza reported annually develop into complications that cause the death of 250-500 thousand people, especially among the population groups at risk (children, the elderly and people suffering from chronic diseases). The effects of flu virus are not the same in the world. In industrialized countries, influenza proves to be fatal, especially among those over 65. The effects in developing countries are not known with certainty, however it is estimated that it causes a high%age of deaths among children.
Up to now, three different types of influenza viruses have been identified, constituting the Orthomyxovirus genus: type A and B, responsible for classical flu symptomatology, and type C, of little clinical relevance (generally asymptomatic). Type A viruses circulate in both humans and other animal species and are further subdivided into subtypes, distinguished by differences in surface proteins: emagglutinin (HA) and neuraminidase (NA), to which the response is addressed immune system of infected or vaccinated subjects.
To date, 15 subtypes of emagglutinin and 9 of neuramminidase have been identified. Type B viruses are present only in humans and there are no distinct subtypes in their HA and NA surface proteins. Type C viruses, as already mentioned, give an infection generally asymptomatic or similar to the common cold.
At the basis of the epidemiology of influenza there is the marked tendency of all influenza viruses to vary, that is to acquire changes in surface proteins that allow them to circumvent the barrier constituted by the immunity present in the population that in the past has suffered influenza infection. Changes can occur according to two distinct mechanisms:
1. Antigenic drift
This is a gradual change in the sequence of amino acids that make up proteins that can stimulate an immune response. This phenomenon affects both A and B viruses (but in A more often and more frequently) and is responsible for seasonal epidemics. In fact, the new variants become sufficiently unrecognizable to antibodies in most of the population, so as to make a large number of individuals susceptible to the new strain.
2. Antigenic shift
It is a phenomenon that only affects influenza A viruses and consists in the appearance in humans of a new viral strain with a surface protein (HA and / or NA) belonging to a subtype different from those commonly circulating in humans. Antigenic shifts are due either to reassortments between human and animal viruses (avian or swine) or to the direct transmission of non-human viruses to humans (the most recent example is the one in Hong Kong in 1997). So the sources of the new subtypes are always animal viruses. Since the population has never met these antigens before, under certain circumstances these major changes can cause a sudden and invasive infection in all age groups, on a global scale, which is called the ‘pandemic’.
What is influenza?
At the basis of the epidemiology of influenza there is the marked tendency of all influenza viruses to vary, that is to acquire changes in surface proteins that allow them to circumvent the barrier constituted by the immunity present in the population that in the past has suffered influenza infection. This means that the defenses that the body has developed against flu virus that circulated a year, are no longer effective for the virus of the following year.
For these reasons the composition of the vaccine must be updated every year and surveillance is essential to prepare the vaccine for the following season based on the strains that have had the greatest spread in the last epidemic period. The pandemics occur at unpredictable time intervals and in this century occurred in 1918 (Spanish, subtype H1N1 responsible for at least 20 million deaths), in 1957 (Asian, subtype H2N2), in 1968 (Hong Kong, subtype H3N2). The last influenza pandemic, A (H1N1) pdm09 occurred in 2009.
It is however important to underline that the appearance of a strain with radically new surface proteins, i.e. an entirely different influenza virus from the previous ones, is not in itself sufficient to say that a pandemic has occurred. It is also necessary that the new virus be able to transmit itself from human to human effectively. And the H5N1 subtype viruses isolated from various individuals in Hong Kong in 1997 fortunately lacked this feature. A similar event occurred in 1999, when two children, also from Hong Kong, were affected by flu virus subtype A (H9N2), usually infectious on birds. Even in this case, however, the virus did not pass on to other individuals and no new cases were reported after April 1999.
How is flu transmitted?
Flu virus, generally acquired through contact with other infected people, is found in both saliva and mucus of the respiratory tract and can enter the body through the mucous membranes (mouth, eyes and nose). The virus can be transmitted by air from the time of infection until three or four days after the first symptoms that occur within one to four days of infection. This means that the virus can also be transmitted by seemingly healthy people. It spreads very easily in crowded environments.
The frequency with which cases of flu arise, although very different from season to season, averages around 8% (range: 4-12%) of the general population, each year, while in the age group 0-14 years, which is the most affected, the incidence, on average, is equal to about 22%.
In U.S., influenza occurs during the winter period (mainly between December and March) and is resolved within five to seven days, although coughing and general malaise can last for two weeks or more. Flu is characterized by a sudden manifestation of general and respiratory symptoms: fever (lasting about three days), which manifests itself abruptly, accompanied by chills, bone and muscle pain, headache, severe general discomfort, sore throat., cold, non-catarrhal cough and conjunctivitis.
Fever is generally higher in infections caused by type A viruses, while in those caused by type B, it is kept at lower levels. In infants, in general, fever does not occur but vomiting and diarrhea are observed. Even in the elderly (over 75 years) the fever remains low, the onset of disorders is gradual and mainly involves weakness, joint pains and confusion. The diagnosis of influenza is commonly based on clinical symptoms but certainty can only be achieved by isolating flu virus, which, however, is not carried out except in the context of scientific studies.
Vaccination is the best way to prevent and fight flu, both because they greatly increase the chances of not contracting the disease and because, in the case of development of flu symptoms, these are much less severe and, generally, not followed by further complications. Healthare specialists recommend vaccination to people over the age of 64 and to those who are in close contact with the elderly, to all those at risk of secondary complications due to age or disease.
The most suitable period for vaccination goes from mid-October to the end of December. It is generally not recommended to vaccinate well in advance because the immunity given by this vaccine declines within 6-8 months and, therefore, you could risk being only partially protected in the most risky period (October-February). The administration is intramuscular and, in all those over the age of 12 years, injection should be performed in the deltoid muscle (arm), while for the youngest the anterolateral thigh muscle is recommended.
The most used drugs are symptomatic such as antipyretics (paracetamol) for fever, headache and musculoskeletal pain. Only two drugs with antiviral action, amantadine and rimantadine have been identified, which only act on flu infection caused by type A viruses. However, they should only be used when there are risks of serious complications because they may have side effects like neurological and promote the development of resistant mutant viral strains. Furthermore, they are only effective in 70-90% of cases.
Amantadine is, however, not recommended for children under the age of one. Amantadine and rimantadine can also be used for preventive purposes in people who are at high risk for complications due to influenza and who have not been able to vaccinate (or in which it is supposed not to have developed a good immune response to flu virus). Furthermore, these two drugs do not completely block flu infection so much as to allow the development of a form of natural immunity, even if flu symptoms do not appear.
During 1999, a new drug with antiviral action, zanamivir, was placed on the market in U.S., which is able to reduce the duration of the disease from one to 2.5 days. Zanamivir acts on neuroaminidase (a protein found on the outer surface of the virus that appears to be necessary for the virus to infect cells and to release viral particles after replication within the cell), slowing down the spread of the virus. Unlike amantadine and rimantadine, it does not seem to induce the formation of resistant strains. The drug is active against influenza viruses belonging to both A and B, but should be taken within 48 hours after the onset of symptoms. The drug cannot be given to children under 12 years of age and to women who are pregnant or breastfeeding because there is not yet enough data to ensure their safety in these cases.
Every year he returns and forces millions of people around the world to bed. Assume, that is, the characteristics of an epidemic. In U.S. its maximum spread is between December and February. Influenza is one of the most common diseases. It consists of an infection, caused by a virus, which affects the respiratory system, from the nose to the lungs. It is very contagious and spreads rapidly by air, especially in crowded environments, such as schools, offices or nursing homes. It is not a serious disorder: in most cases the disease runs out within a week, even if the exhaustion can be prolonged for a longer period. If left untreated, however, flu can also cause serious complications.
The viruses responsible for the infection belong to the family of the orthomixoviruses and are distinguished from those of other infectious disorders by two characteristics. First of all because there is not a single type of virus, but there are different ones, A, B and C: the first two are responsible for the classic form of influenza, while the type C, generally asymptomatic, causes a similar infection to the cold.
> Type A viruses circulate both in humans and in other animal species (birds, pigs, horses) and are in turn subdivided into subtypes. Usually the virus is transmitted from birds to pigs and from pigs to humans.
> Type B viruses are present only in humans and there are no distinct subtypes. Secondly, influenza viruses are mutants, that is, they change from year to year, thus forcing our immune system to produce new antibodies that can tackle and defeat them. For example, if a person has passed a type A virus infection the previous year, it is not sure to be immune to relapses the following year: the same virus can be modified and the organism, to neutralize it, must produce new antibodies.
> Influenza viruses survive only in the upper respiratory tract cells: nose, pharynx and larynx. This means that if during or following an influenza the bronchopneumonia develops, the responsible cannot be flu virus: in this case the disease is due to the bacteria that, taking advantage of the weak state of the person, attack the bronchi and lungs.
>The virus that infects wild and domestic birds (including chickens) is called ‘avian flu virus’: it usually does not infect humans, although in 1997 there were some sporadic cases of bird flu in people in Hong Kong who had direct contact with infected animals (breeders, slaughterers and veterinarians). The bird flu virus, however, is not transmitted through the ingestion of infected meat or eggs.
Types of epidemic
A characteristic of influenza is the tendency of viruses to continuously change their characteristics over time: if the changes are profound under certain circumstances, there can be important consequences for the population that, having never met the new virus, is poorly immunized and sick more easily. This phenomenon can coincide with the appearance in all age groups of major global epidemics, called ‘pandemics’.
The pandemics occur at unpredictable time intervals and in this century occurred in 1918 (Spanish, subtype H1N1), in 1957 (Asian, subtype H2N2) and in 1968 (Hong Kong, subtype H3N2). The most severe, the Spanish, has caused at least 20 million deaths. The appearance of a virus strain with radically new surface proteins is certainly not sufficient to say that a pandemic has occurred. It is also necessary that the new virus be able to transmit itself from human to human effectively.
But here are some characteristics of influenza infections:
- pandemic: widespread throughout the world
- epidemic: widespread at local level
- endemic: sporadic cases that occur throughout the year
- seasonal: in the northern latitudes occurs in winter, in the southern ones, however, in spring.
From the history of flu
Influenza viruses have probably been an important cause of illness since ancient times. The first flu epidemic is traced back to 1173. The first descriptions of epidemics characterized by flu-like symptoms date back to the 5th cent. a.C., in Greece, and continued throughout the Christian era, highlighting how the flu has been present for thousands of years in the human population. Recently it has been hypothesized that the plague of Athens, which occurred between 430 and 427 BC. and described by Thucydides, was actually an influenza epidemic exacerbated by complications.
The first pandemic attributable to influenza is dated 1580. Since then, 31 pandemics have been described, the largest of which occurred in 1918-19 (the Spanish) when, during three successive waves, 21 million deaths were recorded worldwide. Influenza virus was discovered in 1918 but the first isolation of influenza virus in humans dates back to 1933 in England. Influenza B virus was isolated in 1939 and influenza C in 1950. Influenza viruses have been isolated annually in various parts of the world since epidemics and pandemics since 1940. An influenza A-type outbreak occurs every 2 years, while a type B virus outbreak (which typically has a minor spread and severity) appears every 3-4 years.
The infection occurs from person to person by air: the virus spreads through the droplets of saliva suspended in the air that are emitted with sneezing or coughing from an already affected person, or simply touching with hands surfaces or objects contaminated by sick individuals. The virus usually penetrates through the nose or mouth and rapidly multiplies into the respiratory tract. At the time of infection there is no ill feeling, but in the meantime the virus begins to multiply. In a community or in a region the course of an influenza epidemic episode, after a sudden onset, reaches the acute phase in the course of 3 weeks and therefore tends to go off in a short time (6-10 weeks).
Epidemics caused by influenza virus especially type A may occur periodically in hospital wards or in other closed population groups (such as elderly living in long-term care communities). In these situations the epidemiological characteristics of the disease (short incubation period, airborne transmission) can give rise to epidemics with an explosive character, but of relatively short duration (1-3 weeks). During these epidemics, secondary infections among hospital staff are quite frequent (with attack rates of 20-50%). In turn, hospital personnel can initiate the epidemic by transmitting the infection to susceptible patients.
The first symptoms of influenza
Flu suddenly arises, from one day to the next, without any premonitory symptom. One begins to feel a widespread sense of malaise and feels weak. After the incubation period, which can last from one to three days, the first disturbances typical of this seasonal illness arrive. Flu begins abruptly with the appearance of high fever, which quickly reaches its maximum peak (39-40 ° C) within 12-24 hours, feeling cold and intense chills, with the typical feeling of ‘broken bones’. It also comes the headache, often accompanied by the annoyance for the light (photophobia).
Affected age groups
School-aged children play a central role in the spread of community infection. The increase in school absences is the early epidemiological signal of the onset of an influenza epidemic. Another sign is the increase in visits for feverish respiratory diseases performed by family doctors and doctors who work in the emergency room.
Depending on the affected age group there are some differences in the way flu is presented. In infants and infants little specific symptoms prevail: it occurs with vomiting and diarrhea, often without fever.
The highest incidence of influenza occurs in school-age children and adolescents, while decreasing as the age progresses, so much so that rates of attack are about four times lower in people over the age of 60 than in groups younger than age. In the elderly flu may have different characteristics compared to those of the adult.
At the onset, the symptoms may be more subtle (especially after age 70) with fever rarely exceeding 38 ° C, while behavioral disorders and neurological signs prevail (soporific state, mental confusion, dizziness, urinary and faecal incontinence) that cause also a risk of accidental falls. The highest hospitalization rates are recorded in children aged less than 5 years or in the elderly aged over 65, with 3-6 hospitalizations per 1,000 people during periods of epidemic.
The seasons of influenza
In countries with a temperate climate it usually arrives during winter or early spring. In contrast, in tropical countries, the infection has an endemic course with epidemic episodes that occur even more than once a year. It has not yet been possible to explain the distinct seasonality of the epidemic influenza: according to a reliable hypothesis, the reasons could be the reintroduction of the virus every season and behavioral factors that flu its circulation (for example, the beginning of the school year) and overcrowding). In the temperate countries of the northern or northern hemisphere flu spreads from October to April (with peaks between December and March), while in the southern or southern hemisphere it occurs from April to September-October.
According to some estimates, about 10% of the world’s population (500 million people) annually contract the infection during a typical flu season. In U.S. each year between two and a half million and three million people get sick. The frequency with which cases of influenza arise, although very different from epidemic to epidemic, is around 10-20% of the general population. The epidemiological and virological surveillance system has estimated an incidence in the general population of 5%, while in the age group 0-14 years, which is the most affected, the incidence was about 15%. The incidence can reach as much as 50% of the general population during pandemics.
Flu: diagnosing problems
The clinical diagnosis of flu is not simple. In fact there are numerous micro-organisms (above all viruses but also bacteria) that can cause an acute pathology of the respiratory tract similar to flu. The clinical definition, proposed by the World Health Organization, provides that the patient has the following manifestations: sudden onset of fever (equal to or higher than 39 ° C), muscle pain and respiratory symptoms. It is a simple definition that allows to circumscribe flu symptoms compared to the numerous acute respiratory infections.
From a practical point of view, besides the symptoms, it is important to monitor the local epidemiological course of the infection, that is to say, how many other cases of influenza occur in the community. The certain diagnosis of flu requires laboratory confirmation: direct isolation of the virus is routinely done only by specialized laboratories located at the centers responsible for monitoring the epidemic.
Usually the physician makes the diagnosis of flu based on both the symptoms reported by the patient and the physical examination during the visit, as well as the simultaneous response of many other cases in the community. No further diagnostic tests are necessary. If the doctor suspects a complication of flu, for example a pneumonia, he will prescribe a series of tests, such as blood tests and chest radiographs.
When to contact the doctor
It is necessary to call the doctor if the sick person belongs to one of the risk categories already listed (small children, elderly people, chronic patients) and therefore any complications are feared. You should also consult your doctor in case of difficulty in breathing, chest pain, cough accompanied by greenish-yellow catarrh, particularly strong sore throat or, in general, if after an initial improvement the disease is prolonged for more than a week or it tends to get worse.
The complications of influenza occur when the infection, instead of being limited to the upper respiratory tract, spreads to the bronchi and lungs. The most common complications are bronchitis and pneumonia, usually due to the intervention of ba Particularly fearful for the elderly and for people who suffer chronically from respiratory or cardiac diseases is pneumonia: its appearance raises the hospitalization rates of 3-5 times among adults with high-risk diseases. Influenza are associated with two manifestations of pneumonia: primary viral pneumonia and secondary pneumonia: sometimes the two conditions can coexist.
The most serious form of complication, but also extremely rare, is fulminant pneumonia: at the end of the acute phase of influenza, instead of improving, the situation precipitates, the person falls into a deep prostration and risks dying.
Home remedies for flu
When you get sick of flu, it is good practice to follow certain rules of hygiene and behavior:
- to rest in bed, trying to avoid a climate that is too dry in the environment (for example, using a humidifier)
- do not cover yourself too much, especially in case of high fever, because this favors overheating of the body
- follow a light diet, but be sufficiently caloric
- maintain a good hydration by drinking at least one liter of water a day, fruit juices, broth and milk
- refrain from smoking and drinking alcohol.
If there are no health problems, no special treatment for flu is usually prescribed. In cases of uncomplicated influenza, a therapy is usually used to control the main symptoms caused by influenza viruses. It is also advisable to control the fever so that it does not reach very high values (especially in young children); the rapid and close spills that may result in substantial fluid losses must also be avoided.
The most used drugs, antipyretics and painkillers, are called symptomatic because they bring some relief to the symptoms, but should not be used for too long periods and without medical supervision because they could have side effects. Among the non-steroidal anti-inflammatories, the use of paracetamol which, in addition to lowering fever, reduces headaches and muscular pains should be considered as first choice.
For children and young people under 16, paracetamol alone is recommended. Acetylsalicylic acid can also be used to combat flu, but it should be avoided in children between 3 and 12 years because its intake, in conjunction with a viral disease, could cause Reye’s syndrome, a serious though rare disease that could cause severe brain damage.
The use of drugs against cough must be evaluated on a case-by-case basis and must be taken into consideration especially when the cough is very insistent and such as to compromise (especially in children) feeding and a satisfactory sleep. Among the antitussigeni drugs, those that act by depressing the cough reflex (for example, cloperastine) should be preferred, while the sedative ones (based on dihydrocodeine) should be reserved for situations where the patient’s sedation may also be useful. In the case of productive cough, drugs with expectorant or mucolytic activity are generally used.
Vapor inhalations can alleviate respiratory symptoms and prevent some of the problems induced by drying of membranes and thickening of secretions. The use of antibiotic therapy during flu should not be indiscriminate but requires from the doctor a reasoned assessment of various variables such as the age of the patient, the presence of concomitant diseases that expose to a risk of bacterial complications and above all a careful evaluation of the clinical picture. Antibiotics may be prescribed when bacterial complication is suspected, reported by persistence and severity of symptoms: for example, a high body temperature over 3-5 days, the appearance or increase of expectoration with a purulent appearance, difficulty breathing.
Only two drugs with antiviral action, amantadine and rimantadine have been identified, which only act on flu infection caused by type A viruses. However, they should only be used when there are risks of serious complications because they may have side effects like neurological and promote the development of resistant mutant viral strains. Furthermore, they are only effective in 70 to 90% of cases.
Amantadine is, however, not recommended for children under the age of one. Amantadine and rimantadine (not marketed in U.S.) can also be used for preventive purposes in people who are at high risk for complications due to influenza and who have not been able to vaccinate. Furthermore, these two drugs do not completely block flu infection so much as to allow the development of a form of natural immunity, even if flu symptoms do not appear.
In 1999, a new drug with antiviral action, zanamivir, was placed on the market in U.S., which is able to reduce the duration of the disease from one to 2.5 days. Zanamivir acts on neuroaminidase (a protein on the outer surface of the virus that appears to be necessary for the virus to infect cells and to release viral particles after replication within the cell), slowing down the spread of the virus. The drug is active against influenza viruses belonging to both A and B, but should be taken within 48 hours of the onset of symptoms. It cannot be given to children under 12 years of age and to women who are pregnant or breastfeeding because there is not yet enough data to ensure their safety in these cases.
Prophylactic influenza vaccination is the most effective weapon to prevent influenza and limit its damage. It is especially recommended for elderly people and people at high risk for possible flu complications, such as heart patients, diabetics, asthmatics. In addition to protecting these groups at risk of serious complications, vaccination prevention is able to reduce the possibility of co-circulation of human and avian viruses and to interrupt the chain of transmission of influenza strains that do not have the pandemic characteristic. Every year a specific vaccine is marketed for new varieties of viral strains.
The best prevention of influenza is represented by the vaccine. Vaccination is recommended for all ‘at risk’ categories, but also for those who work in the community (for example hospitals, nursing homes, schools) or who carry out public service work (for example fire fighters and policemen). Anyone who wishes can get vaccinated, buying, after a prescription, the vaccine in the pharmacy.
- try to avoid contagion by keeping away, as far as possible, from crowded places: this applies especially to people at risk, such as children, the elderly, heart patients and lungs or very weak people
- at home let the air change often
- try to keep the immune system efficient, with a diet rich in vitamins, trace elements and minerals. Support for the immune system is particularly necessary for those who lead a stressful life, work hard or are weak.
Influenza AH1N1 virus spreads in the same way as seasonal influenza viruses, i.e.:
1. directly: through the respiratory and saliva droplets emitted with a cough and sneezing;
2. indirectly: through the hands coming into contact with objects and surfaces contaminated by secretions of infected people (door handles, handrails, tables and counters, taps, sports equipment, etc.), and brought to the eyes, nose or mouth without before being washed.
Influenza viruses (including flu AH1N1 virus) live on surfaces for 24-48 hours; however, even after a few hours the infectivity of the viral particles decreases significantly, due to exposure to the external environment and atmospheric agents.
People with influenza, swine or not, are already contagious during the incubation period that preceded the onset of symptoms. The virus can be transmitted from one day before the onset of symptoms up to seven days from the beginning of the symptoms. Children, especially the smaller ones, can instead remain contagious for longer. The re-admission to community life is advisable after 48 hours, and in any case not earlier than 24 hours after the disappearance of the fever (which must be independent from taking drugs to keep it low). This period, however, varies depending on the clinical picture.
The influenza virus affects the mucosa of the upper respiratory tract and attacks the cells of the epithelium of the mucosa itself, within which it penetrates undisturbed. Once inside, it is subdivided into sub-units (‘bits’ of virus): this phase is called ‘eclipses’, because at this moment the virus is not available in the circulation. Subsequently, it replicates, gets rid of the respiratory tree after breaking the cells that housed it, invading other cells repeating the whole cycle and spreading the infection. It follows that large areas of respiratory epithelium die, leaving a fragile and very inflamed mucosa, which therefore begins to produce large quantities of mucus.
Flu, including the swine, begins after 1-3 days of incubation mostly abruptly (more rarely after 24-48 hours of general malaise and headache), with high fever (around 39 ° C), chills, sense of prostration, loss of appetite and refusal of food, intense headache, muscle and joint pain predominantly in the back. Within a few hours, there is also a sneezing, rhinorrhea (‘runny nose’), tearing and photophobia (intolerance to light), faringodynia (sore throat), burning sensation behind the breastbone, first dry cough and then with mucus. Sometimes nausea, vomiting, abdominal pain and diarrhea are present.
Younger children are not able to describe the general symptomatology, which in them can instead be manifested with irritability, crying, lack of appetite. In infants, flu is often accompanied by vomiting and diarrhea, and only exceptionally by fever. Very high fever, red eyes, conjunctivitis, laryngotracheitis and bronchitis are characteristic of influenza in preschool children (1-5 years).
In the elderly, the symptomatology of swine flu may have different characteristics, given the presence of other intercurrent diseases, the weak immune response and the different perception of pain. In them, however, the habit of vaccinating helps to alleviate the severity of symptoms that are, especially in the elderly, often devious, with a low fever, inability to maintain posture, drowsiness, motor incoordination and incontinence of urine and faeces. The other diseases present in the elderly may worsen the clinical picture, and cause metabolic decompensation of diabetes, heart failure, respiratory failure, etc.
An analysis of over 600 cases of influenza A – H1N1 in the USA showed that the most frequent symptoms were: fever (94% of cases), cough (92%) and sore throat (60%). In addition, 25% of patients had a gastrointestinal symptomatology (diarrhea and / or vomiting) that is usually characteristic of the pediatric age, while in the adult one varies from 6 to 10%. However, the epidemiological data provided in June 2009 showed a lower presence in the elderly population of the H1N1 influenza compared to the seasonal one. The course is short-lived: after 2-4 days the fever disappears, with sweating and remission of the symptoms. The respiratory symptoms of swine flu may persist for a long time (about 20 days); the persistence of fever, instead, must make one suspect a complication. After the remission of symptoms, convalescence follows, characterized by profound asthenia (fatigue, easy fatigue) and coughing, which can last for 1-3 weeks.
Swine flu complications
In the onset of complications, the immune situation of the affected person plays a fundamental role, especially influenced by other diseases already present at the time of infection with the H1N1 virus. Complications may be due to direct action of the virus or over bacterial infections.
- bronchitis (10% of cases): due to the dissemination of the virus to the farthest branches of the bronchial tree. It is characterized by fever, sputum (mucus) mucous, sometimes streaked with blood;
- pneumonia: begins in the second or third day with dyspnea (air hunger), cyanosis (bluish skin color due to lack of oxygen), sputum with abundant blood, chest pain, sweating, tachycardia;
- other (very rare): myocarditis, encephalitis, involvement of nerve structures (myelitis, neuritis, radiculitis, poliradicolonevrite).
- bronchiolitis: characterized by dyspnoea, tachypnea (increased frequency of breath), cough with frothy or blood-streaked sputum, rapid appearance of cyanosis, agitation;
- acute stenosing laryngitis (viral croup): with ‘barking’ cough (because it looks like a dog howling), dyspnoea especially in inhalation, cyanosis, agitation, pallor, sweating.
Bacterial complications of swine flu are generally supported by germs such as staphylococcus, pneumococcus, streptococcus, Haemophilus influenzae. They appear after 2-15 days, even in convalescence and are more frequent in the respiratory tract, for the implantation of these germs on the fragile mucosa injured by the action of the virus.
Possible complications are: bronchitis, pneumonia, bronchopneumonia, but also otitis and sinusitis; they occur mainly in children and in the elderly, in subjects with weak immune system, cardiopaths or carriers of respiratory diseases (asthma, emphysema, chronic bronchitis). The picture is characterized by the persistence of fever, cough with sputum full of mucus or pus.
Swine flu treatment
Routine use of antiviral drugs (Tamiflu) for the treatment of influenza syndrome is not recommended due to the low relevance of outcomes (the decrease of about one day of fever in adults and half a day of fever in children), adverse events – sometimes severe – and the phenomena of resistance associated with their use.
The use of antibiotics in flu syndrome without complications is also recommended, as well as for flu-like sore throat, unless there is evidence to determine the bacterial origin (whitish patches of the tonsils and positive pharyngeal swab) for bacteria). The treatment of uncomplicated swine flu forms involves rest, antipyretics and analgesics (drugs that lower fever and remove pain), cough syrups and liquid administration, better if sweetened. Antibiotic therapy must be immediate in lung bacterial complications.
The use of antipyretic and anti-inflammatory drugs should not be aimed at the continuous control of fever, but at the need to offer relief to the patient’s illness and its difficulty in managing it. Paracetamol (especially recommended for its lower gastric lesion), Ibuprofen and Diclofenac are the most used drugs for the treatment of fever and painful symptoms of adults. In patients with increased risk of heart and vascular disease, the use of Paracetamol is recommended, while for those already on low-dose Aspirin therapy, a valid alternative is to increase the dose of the same until the minimum required dose is reached. to achieve the desired antipyretic and analgesic effect.
In children, on the other hand, Ibuprofen and Paracetamol are recommended, but Aspirin is not recommended due to its association with Reye’s syndrome, characterized by encephalitis and fatty liver.
Vaccination for H1N1 in U.S.
In particular, those affected by: chronic diseases affecting the respiratory system (asthma, bronchopulmonary dysplasia, cystic fibrosis and COPD) are considered to be at risk; diseases of the cardiocirculatory system (congenital and acquired cardiopathies); diabetes mellitus and other metabolic diseases; kidney disease with renal failure; diseases of the blood and lymphatic system; neoplasms; severe liver disease and liver cirrhosis; congenital and acquired diseases that lead to a deficient production of antibodies; suppression of the immune system induced by drugs or HIV; chronic inflammatory diseases and intestinal malabsorption syndromes; pathologies linked to an increased risk of aspiration of respiratory secretions (neuromuscular diseases, obesity with body mass index BMI> 30).
Depending on the availability of the vaccine, other categories of subjects not considered at risk may also be included in the program during the vaccination campaign. At present, no indications have been provided regarding the vaccinations of pregnant women.
The pandemic influenza vaccine (H1N1) available today in U.S. is called Focetria, and is produced by the Novartis pharmaceutical company. The other two available vaccines are Pandemrix, produced by GlaxoSmith Kline, and Celvapan by Baxter.
Focetria active ingredient: surface antigens of influenza virus (hemagglutinin and neuraminidase) of the strain analogous to the A / California / 7/2009 virus strain (X-179A).
Adjuvant: the vaccine contains an adjuvant (MF59C.1) necessary to stimulate a more effective immune response. MF59C.1 is an oil / water emulsion containing 9.75 milligrams of squalene, 1,175 mg of polysorbate 80 and 1,175 mg of sorbitan trioleate in citrate buffer.
Excipients: thiomersal (only in the multi-dose vial), sodium chloride, potassium chloride, potassium phosphate monobasic, sodium dihydrate phosphate dihydrate, magnesium chloride hexahydrate, calcium chloride dihydrate, sodium citrate, citric acid, water for injections.
Contraindications and unwanted reactions to vaccination
The administration of the vaccine is contraindicated in subjects with hypersensitivity to egg proteins or to other components of the vaccine. Influenza vaccination should be postponed for one to two weeks in the event of ongoing febrile manifestations or other acute illnesses of any kind. People taking immunosuppressive drugs (depressing the immune system) can respond to influenza vaccination in a suboptimal manner; therefore it would be appropriate, when possible, to postpone the vaccination for at least one month after the interruption of treatment. Treatment with cortisone for local use (ointments or gel) or for general use (tablets or punctures) at low dosage is not a reason to postpone flu vaccination.
HIV seropositivity is not a contraindication to the administration of influenza vaccination although, HIV-positive subjects with low CD4 + T cell values, the administration of the vaccine may not be protective and a second dose of vaccine in these subjects does not improve the response so substantial. No substantial increases in virus replication, reduction of CD4 + T lymphocytes, and progression to AIDS have been demonstrated in HIV positive subjects undergoing vaccination.
In individuals with autoimmune diseases, flu vaccine should only be administered after a careful assessment of the risk-benefit ratio. Manifestations of immediate hypersensitivity, or neurological reactions following a vaccine administration are an absolute contraindication to subsequent doses of the same. Influenza vaccination is not contraindicated in nursing mothers.
The most frequently reported side effects after administration of influenza vaccine consist of pain, skin erythema, swelling, pain, redness and heat at the injection site.
Other unwanted reactions reported frequently, especially in people never vaccinated previously, consist of general malaise, fever, myalgia (muscle pain), with onset 6 to 12 hours after administration of the vaccination, and lasting for 1 or 2 days.
There have also been allergic reactions such as urticaria and asthma, especially in people with hypersensitivity to egg proteins or to other components of the vaccine. After influenza vaccination, other adverse events such as transient decreases in platelet counts, neuralgia (pain due to nerve root involvement) and neurological disorders have been reported (although no correlation between influenza vaccine administration and such events has been demonstrated). Adverse reactions to vaccination should always be reported by the primary care physician to the Ministry of Health through the compilation of a specially prepared form.
The reticence of many people to get vaccinated comes from some information regarding the adjuvant used in the preparation, namely the squalene. It all stems from a research published in February 2000 in the journal Experimental Molecular Pathology which said that Gulf War veterans have contracted a syndrome bearing this name (Gulf War Syndrome- GWS) after receiving anthrax vaccines which contained squalene and it was seen that 95% of those who developed this syndrome had developed antibodies against squalene.
MF59 (the squalene adjuvant present in the Focetria vaccine and also in Pandemrix, but not in Celvapan), was an ingredient not approved in experimental anthrax vaccines, and has since been linked to the potential onset (after years) of autoimmune diseases such as rheumatoid arthritis, fibromyalgia, systemic lupus erythematosus, multiple sclerosis, Raynaud’s phenomenon, Sjogren’s syndrome, oral ulcers, thyroid problems, etc.
All this has not been sufficiently demonstrated, and the correlation between squalene and the onset of these diseases has never been ascertained, since the studies carried out on patients vaccinated for swine flu are still too short to be able to give any kind of certainty.
There is currently no medical science that can guarantee us the safety of swine flu vaccines (H1N1). However, since it is an influenza that can cause major complications in those at risk, especially those with respiratory and cardiac problems, vaccination is recommended, because the side effects of the vaccine would be lower than those resulting from one of the complications of flu.
There has also been much discussion about the economic question linked to this flu, so much so as to call it ‘The affair of influenza A – Pandemic of gain’. Many have questioned the economic interests behind the swine flu, and in particular have wondered why in the world every year the common flu kills half a million people, measles and pneumonia 10 million, malaria and diarrhea two million, but the news does not say anything about this.
And instead, years ago, with the H5N1 flu (avian), and today with the H1N1 (swine), the world news have been flooded with news and warning signs. Bird flu has caused the death of a few hundred people around the world, but it caused so much sensation because, it is said, the pharmaceutical company producing Tamiflù (an antiviral) has sold millions of doses to Asian countries, and also to the British government, which bought 14 million doses for prevention in its population.
With the flu of the chickens yesterday and the pigs today, the big pharmaceutical companies that market the antivirals and the vaccines, have obtained and are still having a huge gain. It is therefore said that the ‘panic effect’ created in the population was a marketing tool to sell vaccines and antivirals, and therefore it is a real deal at the expense of citizens.
What is avian influenza?
Bird flu is an infectious and contagious disease that affects domestic and wild birds, often causing serious illness and even the death of the animal. Type A influenza viruses responsible for bird flu can also infect other animals and in some cases humans. Not surprisingly, among all, the one that raises the most concerns – having caused several cases of illness, even fatal, in humans – is the A / H5N1 virus, to which the dangerous strain H7N9 has recently been added.
The viruses that cause bird flu are therefore of different types. Their marked pathogenicity lays the foundations for frequent mutations and recombination phenomena; In practice, avian influenza viruses have a tendency to mutate and exchange genetic traits to create new viral subtypes. In recent years, outbreaks of bird flu have occurred in Asia, Africa and part of Europe. The two main risks to human health deriving from the disease are:
- direct infection, when the virus is transmitted from an infected bird to humans
- mutation or recombination of the virus in a highly contagious form for humans, more easily transmissible from person to person.
Influenza viruses circulating in animals pose a potential threat to human health. Human beings can indeed become ill when infected by some animal viruses, including the avian influenza virus (with its subtypes H5N1, H9N2, H7N7, H7N2 and H7N3) and the swine flu virus (subtypes H1N1 and H3N2). The main risk factor for human infection appears to be close contact with infected animals, live or dead, or with their feces and respiratory secretions.
Most avian influenza viruses do not cause disease in humans. However, some strains are zoonotic, meaning they can infect humans and cause disease. The best known example is the H5N1 avian influenza virus, currently circulating in poultry in some regions of Asia and Africa. Unlike seasonal human influenza, the H5N1 aviary does not spread easily from person to person. From the first human case in 1997, the H5N1 virus killed almost 60% of those infected. As of 2011, this highly pathogenic virus is considered endemic in six countries (Bangladesh, China, Egypt, India, Indonesia and Vietnam); this means that the virus can be commonly found in poultry circulating in these countries. Sporadic outbreaks have also occurred in other countries.
In addition to H5N1, other subtypes of avian influenza viruses, including H7N7 and H9N2, have infected humans: some of these infections have been severe and have resulted in deaths, but for the most part they have been mild or even subclinical.
On 1 April 2013, in China, the first known human cases of H7N9 bird flu infection were reported. These have been associated with a serious, potentially fatal respiratory disease. Avian influenza viruses have been isolated from more than 100 different species of wild birds from around the world, including water hazards or waterfowl (gulls, ducks, geese and swans).
It is suspected that the infection can spread from these natural carriers to domestic fowl (chickens, turkeys, ducks) and other farm animals such as pigs, horses, dolphins and whales. Birds play an important role as a source of food and livelihood in many countries affected by the bird flu virus. This is why the WHO and other bodies in the health sector are working to identify and reduce risks to animal health and public health in national contexts.
Avian influenza: symptoms and complications
The signs and symptoms of bird flu can be variable. The onset of the disease occurs after a variable incubation period, from 1 to 7 days from the time of infection. In most cases, the symptoms resemble those of conventional influenza, namely:
Some people also experience nausea, vomiting or diarrhea. In some cases, a slight ocular infection (conjunctivitis) is the only expression of the disease. Symptoms can worsen and evolve into a severe respiratory disease that can be fatal. In February 2005, researchers in Vietnam reported human cases of bird flu in which the virus infected the brain and the digestive tract.
People with bird flu may develop life-threatening complications, including:
- Pulmonary collapse;
- Respiratory failure;
- Renal dysfunction;
- Heart problems;
- Neurological alterations.
- Low pathogenic viruses and highly pathogenic viruses
Avian influenza viruses (influenza A viruses) belong to the Orthomyxovirus genus. Their surface antigens H (emagglutinin) and N (neuraminidase) may vary, giving rise to different viral phenotypes, named with the initials H (n) N (n). The various strains are classified in low pathogenic viruses (LPAI, Low Pathogenic Avian Influenza) and in highly pathogenic viruses (HPAI, Highly Pathogenic Avian Influenza), based on viral structure, genetic criteria and specific molecular pathogenesis.
Bird flu viruses are mostly low-pathogenic, usually associated with mild disease in poultry. In contrast, highly pathogenic viruses can cause serious illness and high mortality in birds.
LPAI viruses have the potential to become HPAI viruses. This behavior has been documented in some poultry outbreaks. The avian influenza viruses of the H5 and H7 subtypes, including H5N1, H7N3 and H7N9, have been associated with HPAI and the human infection caused by these viruses can range from mild (e.g.: H7N3) to severe and fatal manifestations (H5N1 and H7N9).
Human disease caused by LPAI infection has very mild flu-like symptoms at the onset. Examples of LPAI viruses that can infect humans include H7N7, H9N2 and H7N2.
How is avian flu contracted?
Bird flu affects many wild migratory water birds and can spread to domestic fowl, such as chickens, turkeys, ducks and geese. Bird flu mostly affects wild birds that usually do not get sick but act as reservoirs and can get rid of viruses through faeces and respiratory secretions. As a result, they can be very contagious for domestic fowl with which men come into contact with greater ease.
The disease is transmitted through contact with the feces of an infected bird or with its secretions coming from the nose, mouth and eyes. The most common transmission modalities are the fecal, gold-nasal and conjunctival transmission. Outdoor markets or farms, where eggs and birds are sold in conditions of overcrowding and precarious hygiene, can represent foci of infection and spread the disease in larger communities. The infection can be contracted simply by touching the contaminated surfaces.
The avian flu virus (H5N1) finds the best conditions for its survival in low temperatures, managing to resist in the environment for long periods (over 30 days at 0 ° C), and indefinitely in frozen material. On the other hand, it is very sensitive to the action of heat (at least 70 ° C) developed during food cooking.
Infected birds can continue to release the virus in their feces and saliva for 10 days from the infection. The virus can be inactivated immediately by UV rays and common disinfectants, and is sensitive to heat. According to the Food and Drug Administration, bird flu is not transmitted by eating eggs of infected birds or properly cooked poultry meat. The consumption of poultry meat is safe if the cooking method allows an internal temperature of at least 74 ° C to be reached. The eggs must be cooked until the egg yolk and egg white are completely congealed.
The greatest risk factor for bird flu seems to be close contact with sick birds or with surfaces contaminated by feathers, saliva or infected excrement. The meaning of ‘close contact’ differs from culture to culture. Some people contracted the H5N1 virus while cleaning or plucking infected birds. In China, there have been reports of infection in the markets of live animals by inhalation of materials dispersed in the aerosol. It is also possible that some people have been infected as a result of bathing in water contaminated with excrement of infected birds. Only in a few cases, bird flu was transmitted from one infected human to another by direct contact.
People of all ages can get bird flu. If a susceptible individual or animal is infected at the same time by the avian influenza and human influenza virus, a gene recombination may occur. Even without exchanging genes, the H5N1 virus still has the potential to mutate into a form that more easily infects humans, spreading rapidly around the world. When this happens pandemics are triggered, which in the past have caused very high numbers of patients, hospitalizations and deaths. When this event occurs again the health authorities may be able to avoid the pandemic: H5N1, for example, is sensitive to the latest flu drugs and a vaccine has already been created and stored by the World Health Organization.
Avian flu diagnosis
Bird flu is usually diagnosed through a swab that collects secretions from the nose or throat within the first days of the disease, after the onset of symptoms. The sample is sent to a laboratory, where avian influenza viruses will be searched and identified using a molecular test or suitable cultures. Depending on the type of survey, the results may be available after a few hours or weeks. In late stages of the disease, it may be difficult to identify an avian influenza virus using these methods, but it is still possible to diagnose the infection by looking for evidence of the immune response against the viral agent. Diagnostic imaging can be useful for assessing lung conditions and establishing the correct diagnosis and treatment options.
Avian flu drugs
For the treatment (and prevention) of a human infection with avian influenza, the prescription of oseltamivir or zanamivir is currently recommended. In particular, the available analyzes for H5N1 indicate that most viruses are sensitive to these two anti-influenza drugs, known as neuraminidase inhibitors. Oseltamivir and zanamivir shorten the symptomatology by a couple of days and reduce further viral multiplication in the cells.
However, episodes of drug-resistance have been reported in some human cases of H5N1 bird flu. These antiviral drugs must be taken within two days of the onset of symptoms, which can be logistically difficult worldwide, if there is a widespread epidemic. Laboratory studies suggest that drugs approved to treat the human influenza virus (example: amantadine and rimantadine) should also act in case of avian influenza infection, but further studies are needed to determine its efficacy.
Currently, the best way to prevent bird flu is to avoid potential sources of virus exposure. Most human infections have occurred following prolonged and direct contact with infected poultry or (more rarely) with sick patients.
Some measures have been adopted with the aim of preventing the disease from spreading in the territory. These include the ban on the importation of poultry meat and related products from countries affected by the epidemic and the obligation to label poultry carcasses, indicating the code and the identification number of the breeding of origin. Persons working with poultry or exposed to bird flu outbreaks are encouraged to follow the recommended biosecurity standards and to implement infection control practices; these include the use of adequate personal protective equipment and hand hygiene care.
Avian flu vaccine
To prevent infection, the Food and Drug Administration approved a vaccine formulated against many of the H5N1 avian influenza varieties. This vaccine is not available to the public, but is ready and stored by the WHO, which will distribute it in the event that an H5N1 virus initiates an avian flu pandemic. The purpose of any vaccination is to provide limited protection until another vaccine is designed against the specific form of the mutated virus (approximately within three to four months).
- Subjects traveling to Southeast Asia or any region with sporadic outbreaks of bird flu should follow the following recommendations:
- Avoid contact with domestic birds. If possible, avoid rural areas, small farms and open-air markets.
- Wash hands. This is one of the easiest and best ways to prevent infections of any kind.
- Use an alcohol-based disinfectant (at least 60%) to wash surfaces or dishes touched by patients or persons with suspected flu.
- Do not consume meat or raw or undercooked eggs
- Before leaving, it is useful to ask the doctor for a flu shot. It does not specifically protect against avian influenza, but may help reduce the risk of simultaneous infection of human and avian influenza viruses.
Proper handling and cooking of poultry and eggs cancels the risk of contracting bird flu by feeding on such food. Heat destroys avian viruses, so properly cooked poultry does not pose a health threat. By implementing certain practices during handling and preparation of poultry, it is also possible to avoid the spread of Salmonella or other harmful bacteria that can infect foods. Buying guaranteed poultry by origin and provenance, avoid cross contamination. Use hot water and soap to wash chopping boards, utensils and all surfaces that have come into contact with raw poultry. Wash hands with soap and warm water for at least 20 seconds before and after handling raw poultry and eggs. Separate the raw food from the cooked in the fridge.
Cook the chicken thoroughly until the escaping juices are transparent and a minimum internal temperature of at least 74 ° C is reached. Avoid the raw eggs. Eggshells are often contaminated with bird droppings, so to prevent avian flu it would be advisable to avoid foods containing raw or undercooked eggs.