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Why does the flu virus affect some people worse than others?

The answer to this question, researchers from University of California – Los Angeles find, is due to the first flu strain the people encounter during their childhood. This strain determines how the human body responds to other strains encountered during adult life.

The general finding, which challenges earlier immunological research, is that exposure to influenza viruses during childhood confers people which a level of protection throughout their lives against other influenza viruses. This is a theory termed “immunological imprinting.”

To assess the issue of the impact of influenza in relation to the age of a person and their previous history, the researchers studied health data drawn from the Arizona Department of Health Services.

The researchers also noted how two subtypes of influenza virus: H3N2 and H1N1, have generally been the leading causes of seasonal outbreaks in recent years. Of these two strains, H3N2 causes the majority of severe cases in high-risk groups; and H1N1 tends to affect younger people and is associated with fewer deaths.

The patient data indicates that those exposed to the less severe strain, H1N1, during childhood tend to be less impact, in terms of flu severity, when exposed to H1N1 as adults compared with those in the population who were first exposed to the H3N2 viral strain. The data analysis also revealed those who were first exposed to H3N2 received extra protection against strains of H3N2, should infection occur in later life.

The differences between the two viral strains is thought to occur because H1N1 and H3N2 are found on two separate branches on the influenza “family tree”. This finding opens up new avenues for influenza research and may assist with vaccine development.


The same research group also report on travel-related screening for the novel coronavirus 2019-nCoV, which originated from the Wuhan province in China and which has been dominating global headlines.

The scientists have found that the process for screening travelers being used by government agencies is not very effective in terms of detecting the particular coronavirus. The research suggests that only 50 percent of infected travelers, on average would be detected through the protocols being adopted.

Research paper

The findings have been reported to the journal PLoS Pathogens. The research paper is titled “Childhood immune imprinting to influenza A shapes birth year-specific risk during seasonal H1N1 and H3N2 epidemics.”

Written By

Dr. Tim Sandle is Digital Journal's Editor-at-Large for science news. Tim specializes in science, technology, environmental, and health journalism. He is additionally a practising microbiologist; and an author. He is also interested in history, politics and current affairs.

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