First US Outbreak of H7N9 Bird Flu Since 2017 Spurs Health Worry

bird flu spread

The first outbreak in the US of deadly H7N9 bird flu strain since 2017 was detected in a Mississippi poultry farm, raising fresh health concerns.

H7N9, which is separate from the H5N1 strain that has been sweeping through flocks across the US, was detected in a commercial broiler breeder chicken flock in Mississippi, the World Organization of Animal Health said in a Monday alert. The outbreak, confirmed on a Noxubee County farm last week, affected 47,654 birds, according to the report.

The flock is being culled, and the US Department of Agriculture is investigating. The strain was last detected on two poultry farms in Tennessee in a 2017 outbreak that also affected commercial and backyard flocks in Alabama, Kentucky and Georgia.

The subtype, first found over a decade ago in China, “is of concern because most patients have become severely ill,” though it “does not appear to transmit easily” between people, according to the World Health Organization. Most human infections have occurred after exposure to live poultry or contaminated environments. More than 600 people in China have died of H7N9 since 2013, out of a total 1,568 confirmed infections, according to the World Health Organization.

Researchers in Thailand in 2013 indicated that the mortality rate in H7N9 was lower than for the H5N1 strain. But the virus appeared to spread faster, potentially making it more severe were it to mutate.

The case in Mississippi was likely caused by wild birds and is a “fully North American” virus, unrelated to the H5N1 strain, the US Department of Agriculture said in a statement.

The ongoing H5N1 outbreak that began in 2022, roiling US poultry farms and sending egg prices soaring, has affected roughly 167 million birds and infected 70 humans, including one death. The Trump administration has already announced a five-point plan in response, including boosting egg imports and funding biosecurity measures.