We are in the middle of the flu season and it is certain that several co-workers have “fallen”, a family member has spent a few regular days or even we ourselves have had to stay at home “doubled” by the happy virus. It is also more than possible that around us we see people who are as if nothing, who have not been infected or who have had symptoms, they have been very mild. Why is this happening? Why some yes and others no? Part of the answer, according to a new study published in PLoS Pathogens , is related to the first strain of flu we get in childhood. Their findings could help improve strategies aimed at minimizing the effects of seasonal flu.
Scientists at the University of California, Los Angeles (UCLA) and the University of Arizona have found that exposure to influenza viruses during childhood offers people partial protection for the rest of their lives . Biologists call this “immunological imprinting.”
The discovery demolishes the widely held belief that previous exposure to a flu virus protects little or nothing from strains that can be passed from animals to people, such as avian and swine flu. It is precisely these strains that are of most concern globally because they could mutate and not only easily jump from animals to people but also spread more quickly between humans.
In the research, the scientists studied two subtypes of the flu virus: H3N2 and H1N1, which are mainly responsible for seasonal flu outbreaks in recent decades. The first usually affects the elderly and is the one that causes the greatest complications and most deaths from influenza. H1N1 usually affects young and middle-aged people and causes fewer deaths.
The researchers analyzed health records that the Arizona Department of Health Services obtains from private doctors and hospitals and found a pattern. They found that people who were first exposed to the less serious strain, H1N1, during their childhood were less likely to end up hospitalized if they encountered H1N1 again later than people who were exposed to H3N2 for the first time. The same thing happened to those who were exposed to H3N2 for the first time, that is, they were more protected against this virus throughout their lives. From this they deduced that protection against future infections is much stronger when one is exposed to strains from the same group that has fought before , although it is also true that infection with a strain makes our immune system better prepared to fight infection from another strain.
The research found another pattern that puzzled scientists. It was as follows: People who were exposed as children to H2N2, a strain very close to H1N1, had no extra protection against H1N1 when they encountered it in adult life. It was puzzling because H2N2 and H1N1 are two subtypes found in the same group, and previous studies had shown that exposure to one could, on some occasions, significantly protect the other.
“Our immune system often struggles to recognize and defend itself against closely related strains of seasonal flu, although these are essentially the genetic sisters and brothers of the strains that circulated just a few years ago,” said lead author Katelyn Gostic, who was a student at Ph.D. from UCLA when the study was conducted and is now a postdoctoral fellow at the University of Chicago. “This is puzzling because our research on bird flu shows that deep down in our immune memory we have a certain ability to recognize and defend ourselves against the distantly related genetic third cousins of the strains we saw as children.”
Gostic hopes to find clues that lead to the development of a universal flu vaccine by studying the differences between immunity against bird flu and immunity against seasonal flu. In the first, our immune system is able to protect us effectively while in the other, not so much.
” The last two flu seasons have been more severe than expected, ” said Michael Worobey, co-author of the study and head of the department of ecology and evolutionary biology at the University of Arizona. “In the 2017-18 season, 80,000 people died in the US, more than in the 2009 swine flu pandemic.”
Among the most effective measures to avoid catching the flu or helping to spread the virus are getting vaccinated every year, covering coughs and sneezes with the arm (not the hand), washing our hands frequently with soap and water, and maintaining healthy lifestyle habits. .
