The H5N1 bird flu virus, a major pandemic threat, has historically claimed nearly half of all human cases, but in the US over the past 18 months, only one death was reported among 70 confirmed cases. Researchers believe that people’s immunity to the H1N1 virus, which emerged in 2009 and caused a global pandemic, may be offering some protection against H5N1.
A new study published in Science Translational Medicine found that ferrets infected with influenza A viruses had stronger immunity to H5N1 than those without prior exposure. The researchers also discovered that animals infected with the H1N1 virus developed antibodies that reacted with and potentially protected against H5N1 viruses.
While the findings suggest some level of cross-protection, experts caution that the current understanding is still limited. Yoshihiro Kawaoka, a leading influenza scientist, points to other factors such as differences in the viruses, transmission methods, and human health status as possible explanations for the reduced severity of cases in the US.
However, Richard Webby, a flu expert, believes that some protection from H1N1 may be helping to prevent H5N1 from spreading among humans. The researchers agree that more research is needed to fully understand the mechanism behind this potential cross-protection and to assess the actual threat posed by the bird flu virus.
The study’s lead author, Seema Lakdawala, notes that while pre-existing immunity may offer some protection, it is not enough to prevent an influenza virus from transmitting through a population. Nevertheless, the findings provide hope that if H5N1 were to spread easily among humans, the resulting pandemic might not be as devastating as feared.
Source: https://www.statnews.com/2025/07/23/h5n1-bird-flu-immunity-boosted-by-previous-influenza-a-infection