What is the flu? The flu is caused by viruses other than the common cold and is typically accompanied by symptoms such as fever, body aches, and respiratory symptoms (stuffy nose, cough, or sore throat). Influenza is a highly contagious seasonal respiratory illness that usually strikes between December and March, home page with a peak in February.
There are winters when the flu syndrome causes an epidemic that puts millions of Italians in bed, possibly with serious complications that leave emergency departments overwhelmed with requests. Others in which flu season passes almost unheard of.
The impact of flu season is different every year
It is caused by infection of the respiratory tract (nose, throat, trachea, bronchi, lungs) by influenza viruses.
In general, the flu lasts three to five days, but the fatigue state can last two to three weeks.
The mildest forms can sometimes be confused with a cold: the symptoms are similar, but with the flu they are generally more pronounced and appear very suddenly.
Nasal congestion (discomfort characterized by swelling and discharge from the nose, similar to that associated with sinusitis), sore throat and frequent sneezing are the most common symptoms of a cold, which can cause headaches and cough in addition to breathing difficulties.
Just like the flu; but in the latter case there will be other ailments such as fever, muscle and joint pain, fatigue and weakness. Despite the similarity, cold and flu are two completely different diseases caused by different viruses.
Finally, although the name may be confusing, the so-called stomach flu has nothing in common with the classic flu. The first is actually caused by various viruses and the specific symptoms are nausea, diarrhea and vomiting.
Influenza is a seasonal infectious disease caused by influenza viruses
Three different types of viruses are known, distinguished from each other by the proteins present on their surface: virus A and virus B, causing the classic flu, and virus C, causing an infection that is usually asymptomatic or cold-like. An important feature of influenza viruses is that they have the ability to change the properties of surface proteins.
It is because of this characteristic that flu epidemics occur every year and, unlike many other diseases, you do not develop protection against subsequent infections (immunity); for the same reason, the influenza vaccine must be reconstituted each year with circulating strains and administered annually thereafter.
Contagion occurs from a sick person to a susceptible healthy person through droplets of saliva that are formed and released during coughing, sneezing and phonation (in simple terms); in this case we are talking about direct transmission.
Another way you can get sick is by coming into contact with objects or surfaces (even your hands) on which droplets of saliva or secretions from sick people have settled.
A person with influenza can transmit the disease from 24 hours before the onset of symptoms, usually the virus stops appearing in nasal secretions within 7 days of the onset of the disease; in young children and people with compromised immune systems, but the virus can persist longer.
Symptoms and complications
Influenza is easier to catch in crowded places and with frequent opportunities for contact, so the disease is more prevalent in winter. Influenza is usually a spontaneously resolving illness with a benign outcome. However, in some categories of people, such as children and the elderly, it can lead to complications, which can be serious.
The disease usually has a short incubation period of 1-3 days and is characterized by the sudden onset of symptoms such as:
- High fever accompanied by chills
- Pain in pain
- General nausea
- Muscle pain
- Pain in the joints
- Lack of appetite
All this is followed and accompanied by symptoms related to the respiratory tract:
- Sore throat
- Nasal congestion
In children, the flu can also affect the gastrointestinal tract, causing nausea, vomiting and diarrhea. In general, a person with the flu will recover without any consequences, but there are cases when the disease causes complications that can even be fatal.
Children, the elderly and people with chronic diseases are more at risk of developing complications. The flu becomes more complicated when the infection is no longer limited to the upper respiratory tract, but spreads to deeper passages such as the bronchi and lungs.
Complications of flu include bronchitis and pneumonia; the latter is especially feared by those who already suffer from chronic lung or heart disease, so much so that it increases the number of hospitalizations 3-5 times.
Other complications can be sinusitis and otitis (especially in children).
In addition, influenza in the most vulnerable subjects (for example, heart and lung disease) can cause a rapid worsening of an already existing disease and have a fatal outcome.
Impact on the population
Influenza is a seasonal disease that occurs in our country mainly in winter, with a peak between March and December.
Sporadic infections can also occur outside of regular flu seasons, although the incidence is very low during the summer months.
Influenza is a common reason for medical consultations and hospitalizations and is the leading cause of absence from work (10% of all absences from work) and school , so much so that absenteeism increases by 56% during flu season, resulting in 500,000 lost work days during peak flu season. In Italy, the average absence from work is 4.8 days and each case of flu costs a total of 330 euros.
The disease is also a significant public health problem due to the number of cases that occur each season, which can be more or less high depending on the transmissibility of the circulating influenza virus.
An important problem can be the fact that influenza can present with symptoms very similar to those of other diseases, which leads to a double result: on the one hand, the number of incorrect hospitalizations due to non-influenza syndromes increases, on the other hand, it can happen that signs of pathology are underestimated in terms of morbidity and mortality.