With reports of the first human death from bird flu in the US, some Americans are feeling an uncomfortable flashback to the early days of Covid-19, when infectious disease experts were talking about a new virus that was sending people to the hospital with respiratory infections.

In early December 2024, a group of researchers published an article in the journal Science, entitled "A single mutation in bovine influenza H5N1 hemagglutinin switches specificity to human receptors".

How deadly is the bird flu? The US has reported its first death from avian influenza, H5N1. Here's what to know about bird flu mortality rate and who is at risk.