According to the World Health Organization, the flu affects approximately one billion people every year, of which 3 to 5 million cases are severe. This illness also accounts for 290.000 to 650.000 deaths each year, all over the world. Find out what the flu is, how to distinguish it from a cold, and how to treat and prevent it.
What is the flu?
The flu is an acute respiratory infection caused by the Influenza virus. This virus invades the respiratory system, affecting the nose, throat and, in some cases, lungs. Flu spreads quickly and causes seasonal outbreaks, which can lead to serious complications, especially in high-risk groups. This illness is more common in cold months, but it can occur at any time of the year.
What are the types of flu?
There are 3 principal types of flu, with different characteristics and impacts on public health.
Type A influenza virus
The type A influenza virus is the most common and variable. This virus is responsible for major outbreaks and pandemics. This type’s high mutation rate can lead to the appearance of new subtypes, such as H1N1 and H3N2, which may persist even after immunity has developed through previous infections or vaccination.
This virus can infect various animals, including birds, pigs and, occasionally, other mammals. Transmission between animals and humans can create new strains of the virus. This type was the primary cause of the pandemics in 1918 (Spanish flu), 1957 (Asian flu), 1968 (Hong Kong flu) and 2009 (swine flu).
Type B influenza virus
The type B influenza virus is less variable than type A and is not associated with pandemics, but can still cause seasonal outbreaks and epidemics. As it has a lower mutation rate compared with the type A virus, vaccines can be effective for several years. This virus only infects humans and can cause significant epidemics, especially in vulnerable communities or populations, such as schools and nursing homes.
Type C influenza virus
The type C influenza virus is the least common and usually causes less serious respiratory infections. This type is not associated with any epidemic or pandemic. It only infects humans, and occasionally pigs. The symptoms are similar to a common cold and, most of the time, do not lead to serious complications.
What are the principal causes of the flu?
The primary cause of the flu is exposure to the Influenza virus, which is responsible for infection and spreads in various ways.
When an infected person coughs, sneezes, or even speaks, small droplets containing the virus can spread. Inhalation of these droplets by other people can lead to infection.
The virus can also be transmitted by touching contaminated surfaces. If a person touches a surface where the virus is present and then touches their face, especially the eyes, nose or mouth, they may become infected with the flu.
It is important to remember that the flu virus can survive on surfaces for several hours. Therefore, it can also be transmitted through indirect contact; in other words, if a person touches a contaminated object or surface, and then touches their own mouth or nose, they can be infected.