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H5N1: Do we need to worry about the latest bird flu outbreaks?

BMJ 2023; 380 doi: https://doi.org/10.1136/bmj.p401 (Published 17 February 2023) Cite this as: BMJ 2023;380:p401
  1. Elisabeth Mahase
  1. The BMJ

What is H5N1?

First detected in chickens in Scotland in 1959, and again in geese in southern China and Hong Kong in 1996, H5N1—often called bird flu—is a type of avian influenza A virus that causes a highly infectious and severe respiratory disease in birds.1

The first known human cases were reported in China and Hong Kong in 1997, where transmission from animals to humans led to 18 people being infected, of whom six died. Since then 19 countries have reported more than 860 H5N1 human infections to the World Health Organization from 2003 to 2022. Of these, 53% have resulted in death.

Why is H5N1 in the news now?

While H5N1 has been circulating among birds and poultry in various parts of the world for years, the latest outbreaks have sent warning signals to the scientific community, as the virus seems to be spreading to places previously unreached.

The current clade of the virus, called 2.3.4.4b, was first reported in January 2022 in the US. Since then the US Centers for Disease Control and Prevention (CDC) has reported outbreaks in 47 states, affecting 58 million commercial poultry and backyard flocks.2

However, much of the attention had been on South America, where 10 countries have recorded their first ever cases. Both Argentina and Uruguay have declared national health emergencies after outbreaks, and Peru has seen 55 000 wild birds die in its coastal nature preserves, as well as around 600 sea lions.3 …

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