Are We on the Cusp of a Major Bird Flu Outbreak?

Scientists weigh in on the spread of H5N1 and highlight clues that portend what might come next

A cluster of elongated and circular teal and purple shapes on a black background.
A microscope image of H5N1 avian influenza. Credit: CDC and NIAID

Bird flu, or H5N1 avian influenza, has been circulating across North America since 2022, infecting birds, livestock, wildlife, pets, and humans. Despite 70 documented human cases, there are no known instances of human-to-human transmission — but some scientists are starting to worry that it’s only a matter of time.

Experts from the Harvard Medical School-led Massachusetts Consortium on Pathogen Readiness, or MassCPR, answered questions on March 5 about how H5N1 is spreading and evolving and discussed the state of surveillance efforts, testing, and vaccines.

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“I think we’re all wondering whether this is a minor blip or if we are facing what may turn into an existential threat,” said Bruce Walker, director of the Ragon Institute of Mass General, MIT, and Harvard and member of the MassCPR executive committee.

Experts included:

  • Robert Goldstein, Massachusetts Department of Public Health Commissioner
  • Jacob Lemieux, HMS assistant professor of medicine and infectious disease specialist at Massachusetts General Hospital
  • Jeremy Luban, professor of molecular medicine, biochemistry & molecular biotechnology at UMass Chan Medical School
  • Jonathan Runstadler, professor and chair, department of Infectious Disease and Global Health, Cummings School of Veterinary Medicine at Tufts University
  • Kathryn Stephenson, HMS associate professor of medicine and infectious disease expert at Beth Israel Deaconess Medical Center

Harvard Medicine News: What do we know about the history and evolution of influenza viruses, and specifically H5N1?

Luban: Influenza viruses kill hundreds of thousands of people worldwide each year and have killed tens of millions in pandemics. As influenza spreads from host to host, it gradually accumulates genetic mutations, which is what necessitates an updated flu vaccine each year. Occasionally, an animal is infected with two influenza strains at the same time. When this happens, the viruses swap genes, shuffling their gene segments like a deck of cards to create a new strain. We think this process generates influenza strains like the one that caused the 1918 pandemic.

I think we are living next to a volcano, and it may erupt or it may not. But we need to prepare for the possibility of a pandemic.

Jacob Lemieux

HMS assistant professor of medicine and infectious disease specialist at Mass General