Bird flu jumps from birds to human in Louisiana; patient hospitalized

This is the first human case of bird flu in Louisiana.

A person in Louisiana is hospitalized with H5N1 bird flu after having contact with sick and dying birds suspected of carrying the virus, state health officials announced Friday.

It is the first human H5N1 case detected in Louisiana. For now, the case is considered a "presumptive" positive until testing is confirmed by the Centers for Disease Control and Prevention. Health officials say that the risk to the public is low but caution people to stay away from any sick or dead birds. A spokesperson for Louisiana's health department told Ars that the hospitalized patient had contact with both backyard and wild birds.

Although the person has been hospitalized, their condition was not reported.  The spokesperson said the department would not comment on the patient's condition due to patient confidentiality and an ongoing public health investigation.

The case is just the latest amid H5N1's global and domestic rampage. The virus has been ravaging wild, backyard, and commercial birds in the US since early 2022 and spilling over to a surprisingly wide range of mammals. In March this year, officials detected an unprecedented leap to dairy cows, which has since caused a nationwide outbreak. The virus is currently sweeping through California, the country's largest dairy producer.

To date, at least 845 herds across 16 states have contracted the virus since March, including 630 in California, which detected its first dairy infections in late August.

Human cases

At least 60 people in the US have been infected amid the viral spread this year. But the new case in Louisiana stands out. To date, nearly all of the human cases have been among poultry and dairy workers—unlike the new case in Louisiana— and almost all have been mild—also unlike the new case. Most of the cases have involved conjunctivitis—pink eye—and/or mild respiratory and flu-like symptoms.

There was a case in a patient in Missouri who was hospitalized. However, that person had underlying health conditions, and it's unclear if H5N1 was the cause of their hospitalization or merely an incidental finding. It remains unknown how the person contracted the virus. An extensive investigation found no animal or other exposure that could explain the infection.

No human-to-human spread of H5N1 has been found in the US.

Last month, an otherwise healthy teen in Canada was found to have H5N1 and was hospitalized in critical condition from the infection. It was the first H5N1 human case reported in Canada. Like the case in Missouri, investigators were not able to find an explanation of how the teen contracted the virus. The investigation has since been closed, with no additional cases having been found. Public health officials have stopped providing health updates on the case, citing the closed investigation and patient privacy.

Evolving threat

Infectious disease experts have recently warned that H5N1 may only need to acquire a small number of mutations to become a greater threat to humans. For example, last week, researchers published a study in Science finding that a single mutation in the H5N1 dairy strain would make it better at latching onto human cells. The more the virus circulates around us, the more opportunities it has to accumulate such mutations and adapt to infect our respiratory tracts and spread from person to person.

Influenza viruses are also able to swap genetic segments with each other in a process called reassortment. As flu season begins in the US, a nightmare scenario that experts have raised is if H5N1 swaps segments with the seasonal flu, creating a new, potentially deadly virus with pandemic potential.  For this to happen, a person would have to be infected with the two types of influenza viruses at the same time—something health officials have feared could happen in dairy or poultry workers as the outbreaks continue.

While the human cases of H5N1 detected this year have mostly been mild, the virus has a history of more severity. Globally, H5N1 has had a case fatality rate of 49 percent, according to data collected between 2003 and November 2024 by the World Health Organization. Why the US cases have so far been almost entirely mild is an open question.

12/13/2024, 9:10pm: This post has been updated to include responses from a spokesperson for Louisiana's health department.

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