Prior seasonal flu infections may protect against severe bird flu: Research

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Prior seasonal flu infections may protect against severe bird flu: Research

Synopsis

A study reveals that prior infections with seasonal H1N1 flu could enhance immunity and lessen the severity of H5N1 bird flu, explaining the lower mortality rates in reported cases in the US. Researchers used ferrets to demonstrate the impact of existing immunity on infection outcomes.

Key Takeaways

  • Previous H1N1 flu infections may enhance immunity.
  • H5N1 bird flu severity is influenced by pre-existing immunity.
  • Research utilized ferrets as a model for human responses.
  • Immunity helps in faster virus clearance from nasal passages.
  • Study emphasizes the need for understanding immunity in pandemic risks.

New Delhi, Feb 27 (NationPress) Previous infections with seasonal H1N1 flu may enhance immunity and mitigate the severity of H5N1 bird flu, as indicated by a recent study.

The research, featured in the journal Emerging Infectious Diseases, potentially clarifies why the majority of reported human cases of H5N1 bird flu in the US have not led to fatal outcomes.

Researchers from the universities of Pittsburgh and Emory explored the viruses' potential to transmit among individuals.

Employing a ferret model, they discovered that pre-existing immunity plays a significant role in infection severity. It shielded them from severe illness and mortality caused by a strain of H5N1 bird flu, which is currently prevalent among wild birds, poultry, and cattle. Conversely, ferrets lacking prior immunity encountered more severe illness and higher fatality rates.

“All human flu pandemics arise against a backdrop of pre-existing immunity,” stated lead author Valerie Le Sage, a research assistant professor in microbiology and molecular genetics at the University of Pittsburgh.

“While our model isn’t flawless because the human immune response is complex, it is crucial to consider prior immunity when using ferrets as human surrogates,” Le Sage added.

Ferrets exhibit clinical flu symptoms that closely mimic those of humans, including fever, sneezing, and nasal discharge.

The research team found that among the limited number of ferrets infected intranasally with H5N1, only those with prior exposure to H1N1 survived the infection. Despite similar lung tissue damage, ferrets without prior immunity showed higher fever, greater weight loss, and decreased activity compared to those with H1N1 immunity.

Immunity from earlier infections also appeared to assist the ferrets in expelling the virus from their nasal passages more swiftly and restricted the infection to the respiratory tract.

In contrast, ferrets without immunity displayed signs of systemic infection, with virus particles disseminating throughout the body, including the heart, liver, and spleen.

This study underscores the importance of considering pre-existing immunity in pandemic risk assessments.