Ever wondered why some people can shake the flu easier than others? Part of the answer, according to a new study, comes down to when you were a kid.
The study published in the journal PLOS Pathogens revealed the first flu strain we encounter in childhood sets the course of how our immune system responds to exposures later in life. The findings offer an explanation for why some people fare much worse than others when infected with the same strain of the flu virus.
This study builds on a previous report that found exposure to influenza viruses during childhood gives people partial protection for the rest of their lives.
In the current study, the researchers from UCLA and the University of Arizona set out to investigate whether immunological imprinting could explain people’s response to flu strains already circulating in the human population. The team analysed health records that the Arizona Department of Health Services obtains from hospitals and private physicians.
The researchers looked into two subtypes of influenza virus, H3N2 and H1N1, that have been responsible for seasonal outbreaks of the flu over the past several decades.
They found that people exposed to the less severe strain, H1N1, during childhood were less likely to end up hospitalised if they encountered H1N1 again later in life than people who were first exposed to H3N2, the more severe strain. On the other hand, people first exposed to H3N2 received extra protection against H3N2 later in life.
“Our immune system often struggles to recognize and defend against closely related strains of seasonal flu, even though these are essentially the genetic sisters and brothers of strains that circulated just a few years ago,” lead author Katelyn Gostic said.
“This is perplexing because our research on bird flu shows that deep in our immune memory, we have some ability to recognize and defend against the distantly related, genetic third cousins of the strains we saw as children.”
Gostic said she hopes that by studying differences in immunity against seasonal influenzas we can uncover clues useful to universal influenza vaccine development.
The findings come as the same researchers found that screening travellers for the new coronavirus — that has killed more than 400 people since it surfaced in December — is not very effective and that most infected travellers are undetectable and unaware that they’ve been exposed.
“This puts the onus on government officials and public health officials to follow up with travellers after they arrive, to isolate them and trace their contacts if they get sick later,” Lloyd-Smith, a professor at UCLA, said.
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