Flu is a sudden and rapid (acute) disease that affects the respiratory system.

It is caused by flu viruses and is very contagious. Typically, it is transmitted from person to person through saliva droplets emitted when sneezing, coughing, or talking. You can become infected by directly inhaling the droplets of saliva dispersed in the air or by touching contaminated tools or objects (for example, the telephone handset, toys, etc.) and putting your hands over your eyes, nose or mouth.

People with the flu are contagious as early as a day or two before the symptoms (symptoms) appear, up to three to four days, sometimes even ten, after the onset of the disease. Children and people with a weakened defense system (immune system) can be contagious for an even longer time.

It is a seasonal disease that, in Western countries, occurs during the winter period.

The influenza viruses responsible for the disease in humans are three (influenza viruses type A, B and C) and are constantly changing, especially in the parts that are attacked by the immune system. This continuous transformation makes the immune defenses that do not recognize ineffective. new influenza viruses, transformed compared to those encountered in the past, it is very important, therefore, to avoid the risk of getting sick, to get vaccinated every year, because vaccines are prepared with the viruses that circulate at that moment.

The disease is spread all over the world and causes up to 3-5 million serious cases and between 250,000 and 500,000 deaths each year. In Italy, it is estimated that every year between two and a half million (corresponding to about 4% of the population) to six and a half million (about 11%) people fall ill. Usually, the most affected are children and adolescents. in the age group 0–14 years, among which, on average, 2 million cases occur each year.

The flu should not be confused with the common cold because it is caused by a different group of viruses and the disorders (symptoms) it causes tend to appear more suddenly, are much more intense and last longer.

Severe cases and complications of influenza are more frequent in people over the age of 65 and in individuals with persistent (chronic) diseases such as diabetes, immune or cardiovascular and respiratory diseases. Recent Studies have shown an increased risk of developing a severe form in very young children and pregnant women, however this can also happen in healthy people who do not fit into any of the above categories.

The best defense against the flu is to get vaccinated every year.

In Italy there is a consolidated surveillance system, coordinated by the Istituto Superiore di Sanità, which aims to establish the beginning, duration, severity and intensity of the flu epidemic.



In the event that you become infected and contract the virus, the incubation is usually short enough (about 1-2 days) before the flu manifests itself causing a series of disorders that usually disappear in 3- 4 days. In some cases, however, they can last for one / two weeks.

The flu is characterized by the sudden onset of fever which usually exceeds 38 ° C, with peaks, in children, even up to 39-40 ° C. It is accompanied by cough (usually dry), widespread bone and muscle pain , headache, severe feeling of being unwell (fatigue), sore throat and profuse discharge from the nose. Cough can be very uncomfortable and last 2 or more weeks. Other disorders (symptoms) may also occur, such as, for example, excessive sensitivity and light intolerance (photophobia) and lack of appetite.

Disorders (symptoms) affecting the gastrointestinal tract, such as nausea, vomiting, diarrhea, are not common, as they are usually caused by other types of flu-like viruses, but can occur mainly in children.



Known seasonal influenza viruses are of 3 types, named A, B, and C. Type A viruses are further classified into subtypes based on the combination of virus surface proteins, of which there are different types (18 types of protein H or hemagglutinin and 11 types of protein N or neuraminidase).

Viral subtypes are indicated with the letter A, B or C for the type of virus and with the abbreviations H and a number from 1 to 18 and N and a number from 1 to 9 for the subtype. There are currently two virus subtypes A, named: A / H1N1 and A / H3N2, and two virus subtypes B, identified by the name of the place where they were first isolated, Victoria (Australia) and Yamagata (Japan). Compared to type A viruses, they change less frequently over time. The characteristic of type A influenza viruses is the ability to mutate (modify the structure and the H and N proteins) over time.

Influenza A and B viruses are widespread, circulate around the world, cause annual epidemics and, from time to time, pandemics when new viruses are generated, very different from those in circulation, affecting worldwide and infecting a large part of the world. population. Influenza C viruses are much less common and usually cause mild infections.

The conditions that predispose to being affected by severe forms of influenza and its complications are represented by age (children under 1 year and people over 65) and by risk factors such as, for example, contemporary presence of chronic diseases Recent studies have highlighted an increased risk of disease in pregnant women, however, severe cases of influenza can also occur in healthy people.

There are also avian influenza viruses (avian influenza) which affect various species of wild and domestic birds and can be transmitted to humans following direct contact with sick birds and / or their blood. In these cases, the disorders (symptoms) may not occur or be mild (low pathogenic viruses), or may be severe and generalized, accompanied by dangerous complications and high mortality (highly pathogenic viruses). However, apart from very few isolated cases, these viruses have no still developed the ability to pass from person to person.



People who do not belong to risk categories usually do not need to see a doctor if they are affected by the flu or have flu-like symptoms (symptoms).

The best remedy is to rest in the heat and drink plenty of water to avoid dehydration. In the event of a high fever or to relieve pain, medications such as paracetamol or ibuprofen can be taken, consulting first with the treating doctor. It is advisable to abstain from work or from attending the community (school, gyms, etc.) until recovery .

If, on the other hand, risk conditions or other situations of fragility are present (for example age over 65, pregnant women, presence of chronic diseases), if you develop chest pain, shortness of breath or difficulty in breathing, cough with blood or worsening of the complaints, the attending physician should be consulted immediately. In these situations, the doctor may assess the need for drug treatment (therapy) to treat or prevent complications of the flu. He may prescribe an antiviral drug (oseltamivir and / or zanamivir) to ease the symptoms (symptoms) and help the person to recover faster. Antiviral drugs work by stopping the reproduction (replication) of viruses but they do not cure the flu, but can help to slightly reduce the duration of the disease.

Antibiotics are not prescribed for the flu because they have no effect on viruses but can be useful if a bacterial infection also develops (read the Hoax).



To avoid falling ill with the flu, there are three main prevention strategies: annual flu vaccination, good hygiene (especially hand washing) and the correct use of antiviral drugs.

The flu vaccine

Getting vaccinated is the best way to prevent and fight the flu, both because the available vaccines greatly increase the chances of not getting sick, and because, if flu disorders (symptoms) appear they would be much less serious and, generally, not followed by further complications. (Read the Hoax). In addition, the flu vaccination represents an "important protection measure not only for oneself, but also for close people and reduces access to the emergency room, hospital admissions and medical visits during the periods of greatest diffusion. of the flu.

The flu vaccine is indicated for the protection of people over 6 months of age who do not have specific contraindications to its administration.

In Italy, influenza vaccination is strongly recommended and carried out free of charge for the following categories:

  • people aged 65 or over
  • children over 6 months, teens and adults with:
    • chronic diseases affecting the respiratory system (including severe asthma, bronchopulmonary dysplasia, cystic fibrosis and chronic obstructive pulmonary disease (COPD))
    • diseases of the cardio-circulatory system, including congenital and acquired heart disease
    • diabetes mellitus and other metabolic diseases, (including obese with BMI> 30 and severe concomitant medical conditions)
    • chronic renal failure
    • diseases of the hematopoietic organs (bone marrow, spleen) and hemoglobinopathies
    • tumors
    • congenital or acquired diseases, which involve altered functions of the body's defense system, immunosuppression induced by drugs or the human immunodeficiency virus (HIV)
    • chronic inflammatory diseases and intestinal malabsorption syndromes
    • diseases for which major surgical interventions are planned
    • diseases associated with an increased risk of aspiration of respiratory secretions (e.g. neuromuscular diseases)
    • liver disease, chronic (liver disease)
    • loss of cerebrospinal fluids
    • chronic alcoholism
    • aspleniaanatomical or functional (lack of spleen)
    • candidates for splenectomy, (removal of the spleen)
    • deficiency of terminal complement factors, (causes clotting problems)
    • receiving concentrated coagulation factors, (people with haemophilia, coagulation diseases, at risk of bleeding)
  • children and adolescents on long-term treatment with acetylsalicylic acid, at risk of Reye's Syndrome in case of flu infection
  • pregnant women at the beginning of the epidemic season(read the buffalo)
  • individuals of any age admitted to long-term care facilities
  • doctors and health care personnel
  • family members in contact with people at high risk of complications
  • persons employed in public services of primary collective interest and categories of workers:
    • police forces, firefighters
    • other socially useful categories: armed forces, municipal police, civil protection personnel, post and telecommunications workers, emergency health service volunteers, nursing home assistance personnel, nursery school personnel and schools of all levels
  • personnel who for work reasons are in contact with animals that could be a source of infection with non-human influenza viruses: breeders, people in charge of breeding activities, people in charge of transporting live animals, slaughterers and vaccinators, public veterinarians and freelancers
  • blood donors

Good hygiene

To reduce the risk of getting the flu or infecting other people, one of the strategies is simply good hygiene that prevents the spread of the virus and its transmission through objects or materials (vehicles). Therefore it is essential to wash your hands regularly with warm water and neutral soap or, alternatively, with specific antiseptic formulas; keep surfaces clean, such as the PC keyboard, telephone and handles; cover the mouth and nose when coughing or sneezing or sneezing and coughing in the crook of the elbow, use disposable handkerchiefs, ventilate the rooms at least twice a day because the air exchange removes infectious agents.

Antiviral drugs

The use of the antiviral drugs oseltamivir and zanamivir to prevent influenza is only recommended in the event of a particularly severe epidemic and in unvaccinated people who are at risk of developing serious complications.



Most people recover within a week without needing medical attention, and the flu rarely causes complications in the healthy individual. However, in people at risk it can cause severe forms that can even lead to death. People at risk of complications are pregnant women, children between 6 months and 5 years, the over 65, people undergoing treatments that weaken the immune system or with chronic diseases (asthma, nervous system diseases, chronic bronchitis, cystic fibrosis, heart failure, heart disease, diabetes, cancer, AIDS, etc.), the severely obese.

The most common complication is an overlap of a "bacterial respiratory infection that can cause bronchitis and, in some cases, worsen to pneumonia.

The flu could affect blood sugar levels in people with diabetes, causing hyperglycemia or, in people with type 1 diabetes, diabetic ketoacidosis (a dangerous condition caused by a lack of insulin in the body).

If the flu affects a pregnant woman, premature birth (before the 37th week of pregnancy) or the birth of a low-weight baby may occur. Occasionally, the flu can cause a miscarriage or premature birth.

Less common complications include: tonsillitis, otitis, sinusitis, febrile seizures (especially in children with high fever), meningitis and encephalitis.



Stohr K. Influenza. In: Handbook for the control of communicable diseases, edited by David L. Heymann; Italian edition edited by Giuseppe Marasca. Rome: DEA; 2004

In-depth link

In-depth link

Epicenter. Influence

Higher Institute of Health (ISS). InfluNet network

Ministry of Health. Influence

European Center for Disease Prevention and Control (ECDC), World Health Organization (WHO). Flu News Europe (English)

Europen Center for Disease Control and Prevention (ECDC). Seasonal influenza (English)

World Health Organization (WHO). Influenza (Seasonal) (English)

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