Louisiana resident in critical condition with H5N1 bird flu

The Louisiana resident infected with H5N1 bird flu is hospitalized in critical condition and suffering from severe respiratory symptoms, the Louisiana health department revealed Wednesday. The health department had reported the presumptive positive case on Friday and noted the person was hospitalized, as Ars reported. But a spokesperson had, at the time, declined to provide Ars with the patient's condition or further details, citing patient confidentiality and an ongoing public health investigation. This morning, the Centers for Disease Control and Prevention announced that it had confirmed the state's H5N1 testing and determined that the case "marks the first instance of severe illness linked to the virus in the United States." In a follow-up, the health department spokesperson Emma Herrock was able to release more information about the case. In addition to being in critical condition with severe respiratory symptoms, the person is reported to be over the age of 65 and has underlying health conditions. Further, the CDC collected partial genetic data of the H5N1 strain infecting the patient, finding it to be of D1.1. genotype, which has been detected in wild birds and some poultry in the US. Notably, it is the same genotype seen in a Canadian teenager who was also hospitalized in critical condition from the virus last month. The D1.1. genotype is not the same as the one circulating in US dairy cows, which is the B3.13 genotype.

Deadly version

While it remains unknown how the Canadian teenager became infected, Herrock told Ars last week that Louisiana health investigators found that the infected patient had contact with sick and dead wild and backyard birds thought to be infected with the virus. In today's announcement, the CDC said that:

A sporadic case of severe H5N1 bird flu illness in a person is not unexpected; avian influenza A(H5N1) virus infection has previously been associated with severe human illness in other countries during 2024 and prior years, including illness resulting in death. No person-to-person spread of H5 bird flu has been detected. This case does not change CDC’s overall assessment of the immediate risk to the public’s health from H5N1 bird flu, which remains low.

According to the latest data collected by the World Health Organization, there have been 939 H5N1 cases detected in humans globally between January 2003 to November 2024. Of those, 464 were fatal, for a case fatality rate of 49 percent. This year, the US has tallied 61 human cases of H5N1, almost all of which have been in poultry or dairy workers. Until now, all of them have been mild infections. One unexplained case in Missouri was in a hospitalized patient, but the patient had underlying conditions and the detection of H5N1 was suspected of being an incidental finding. The case in Louisiana is considered the country's first severe H5N1 case and the first case linked to an animal exposure that was not in a commercial operation—in other words, not a dairy or poultry farm.