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.

Bird flu, also known as avian influenza or H5N1, has infected more than 130 million birds over the past two years as it threatened commercial bird operations and recently led to the first human death in the United States.

The U.S. has experienced its first death from H5N1 bird flu. Here’s what happened, plus how concerned you should be, according to doctors.