Could bird flu be quietly spreading undetected worldwide?

Could Bird Flu Be Quietly Spreading Undetected Worldwide?

A strain of H5N1 bird flu, known for killing mammals since 2020, may have developed a concerning new ability — silent transmission in humans. Researchers warn that this could allow the virus to circulate unnoticed and evolve further.

According to a review by CDC scientist Fatimah Dawood and her team, published in JAMA Network Open, asymptomatic infections have been observed in several countries. This suggests the virus might be spreading more widely than previously believed.

H5N1 has already spread rapidly from wild birds to domestic poultry across the world. The jump to mammals raised serious alarm about its potential to infect people more easily. So far, around 21 human deaths have been confirmed since 2020, mostly among those with close exposure to infected animals.

Experts caution that while H5N1 hasn’t yet acquired the mutations needed for easy human-to-human transmission, recent genetic changes improving its ability to infect mammals are concerning. These changes could bring the virus closer to sustaining wider spread among humans.

“This finding challenges the traditional perception that influenza A (H5N1) infection among humans is almost invariably symptomatic and severe.”

If infections remain without symptoms, health authorities may miss chains of transmission, providing the virus time to adapt and spread before detection — potentially increasing the risk of a future pandemic.

Author’s Summary

Silent H5N1 infections could allow bird flu to evolve and spread globally, threatening to ignite a future pandemic before authorities can recognize it.

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Gavi, the Vaccine Alliance Gavi, the Vaccine Alliance — 2025-11-06

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