Missouri Reports First U.S. H5 Bird Flu Case Without Known Exposure to Sick Animals

Missouri is the first U.S. state to report a human case of bird flu, H5 avian influenza, with no known exposure to sick animals, according to the U.S. Centers for Disease Control and Prevention (CDC).

The CDC confirmed on Friday that this is the 14th human case of H5 avian influenza reported in the United States during 2024 and the first case detected through the national flu surveillance system, as opposed to the targeted surveillance efforts focusing on the bird flu outbreak in animals.

The patient, whose identity remains confidential, is being closely monitored by the Missouri Department of Health and Senior Services (MDHSS).

The bird flu patient was hospitalized on August 22 after testing positive for influenza A.

With underlying medical conditions, the patient was treated with antiviral medications and has since recovered, returning home under supervision.

Investigation Underway

Health officials are investigating the source of the infection.

“This is the first case of H5 without a known occupational exposure to sick or infected animals,” the CDC said in a statement, raising concerns about how the virus might be spreading among humans.

So far, there have been no reported cases of bird flu among cattle in Missouri, though outbreaks have been confirmed in poultry across the state. Despite these developments, the CDC’s risk assessment for the general public remains low.

Rising Concerns About Transmission and Mutation

The CDC and other health authorities are continuing to monitor the situation, especially in light of concerns that the virus might have mutated to become more transmissible or virulent among humans.

In an interview with The Guardian in July, Nirav Shah, principal deputy director of the CDC, emphasized the importance of tracking these developments.

“One concern is increasing severity of disease,” Shah said, noting that while previous U.S. cases were mild and occurred primarily among farmworkers, this new case involves an individual with underlying health conditions.

This could indicate that the virus poses a greater risk to the general population, especially those with other health vulnerabilities.

Globally, H5N1 has a high mortality rate, with around 50% of confirmed cases resulting in death. However, many less severe cases likely go undetected, according to health experts.

Person-to-Person Transmission: A Critical Focus

Another major concern is whether the virus could be spreading from person to person.

Shah highlighted that since H5N1 was first observed in humans two decades ago, human-to-human transmission has been exceedingly rare.

However, this case in Missouri, where no known exposure to infected animals occurred, raises red flags for health officials.

“If we were to see individuals with no connection to a farm or chicken exposure developing symptoms, that would be greatly concerning,” Shah said.

“Even if there was no other transmission route identified, that would be a sign that something else is happening.”

Health officials are continuing to trace the patient’s potential exposures and contacts to determine how the virus might have spread.

Bird Flu’s Expanding Reach

Bird flu is typically found in domestic and wild birds, but it has increasingly been detected in mammals, including livestock.

Recently, two indoor cats in Colorado tested positive for the virus, along with house mice.

While no bird flu has been detected in Missouri’s cattle, the virus has been found in poultry and wild birds in the state.

Bird flu can occasionally infect humans through close contact with infected animals or contaminated environments, according to a press release from Missouri health officials.

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