What we know about America’s first “serious” case of bird flu

A lab manager in the molecular diagnostics laboratory prepares milk samples for testing at Cornell University’s Animal Health Diagnostic Center Dec. 10, 2024, in Ithaca.
Photo: Michael M. Santiago/Getty Images

For months, the United States has been battling an ever-growing outbreak of H151, a variant of bird flu. The virus, first discovered in farm and backyard poultry flocks, began spreading to dairy cows in March 2024 and then to people who work with the animals. Health officials have said the overall risk to the American population is low, but the Centers for Disease Control and Prevention has confirmed 61 human cases of bird flu since April 2024. Earlier this month, the US Department of Agriculture ordered testing of the country’s milk supply to begin in six states to detect the presence of the virus. This is a sign of increased vigilance as the virus shows no signs of abating. And on Wednesday, California Governor Gavin Newsom, whose state has confirmed the most cases to date, declared a state of emergency related to bird flu.

Although the majority of reported cases had only mild symptoms, the agency this week reported a new severe case of the virus discovered in Louisiana that resulted in the patient being hospitalized. Here’s what we know about this case and what it means for the general public.

On Wednesday, the CDC issued a news release confirming the presence of a new case of avian influenza in Louisiana and stating that the patient required hospitalization. According to the agency, this is the first case of “serious illness” related to the virus in the United States. The Louisiana Department of Health tells CNN that the patient in question is over the age of 65 and is currently hospitalized in critical condition with a “severe respiratory illness,” but also has other underlying medical conditions.

According to the CDC, the patient’s virus is the D1.1 genotype, which has been detected in wild birds and poultry in the United States and in humans in Washington state and British Columbia, Canada. It is different from the B3.13 genotype, which has been observed in “dairy cows, sporadic human cases in several states, and some poultry outbreaks in the United States.”

“While an investigation into the source of infection is ongoing in Louisiana, it was determined that the patient had contact with sick and dead birds in backyard flocks,” the agency said, noting that this is also the first case of bird flu traced to backyard flocks.

According to the CDC, there have been 61 cases of H151 in the United States since April 2024. In these cases, the patients mostly suffered only mild symptoms. In November, the agency released an update on its outbreak response and wrote about the cases that emerged among farmworkers. In the press release, the CDC described some of her symptoms as “eye redness or discharge (conjunctivitis)” or “mild upper respiratory symptoms.” They noted that none of them were hospitalized.

Despite the appearance of serious symptoms, such a case is “not unexpected,” according to the CDC, noting that other countries that experienced outbreaks of the virus in 2024 and subsequent years have reported cases of severe illness due to avian influenza infection had occurred.

“No human-to-human transmission of H5 bird flu has been detected. This case does not change CDC’s overall assessment of the immediate public health risk from H5N1 avian influenza, which remains low,” the agency said.