Extreme heat may be crucial factor in human spread of bird flu

The extreme heat that has gripped much of the US may have contributed to a spike in bird flu cases. Photograph: Daniel Acker/Bloomberg via Getty Images

Extreme heat may be a crucial factor behind the biggest bird flu outbreak in humans in the US as officials continue to track the virus’ spread.

A heatwave in Colorado likely caused personal protective equipment not to work correctly for workers culling poultry infected with H5N1, a highly pathogenic bird flu. Four people have tested positive for H5N1 and a fifth is also expected to have their case confirmed as bird flu, officials said this week.