missouri

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Bird flu hit a dead end in Missouri, but it’s running rampant in California

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So, in all, Missouri’s case count in the H5N1 outbreak will stay at one for now, and there remains no evidence of human-to-human transmission. Though both the household contact and the index case had evidence of an exposure, their identical blood test results and simultaneous symptom development suggest that they were exposed at the same time by a single source—what that source was, we may never know.

California and Washington

While the virus seems to have hit a dead end in Missouri, it’s still running rampant in California. Since state officials announced the first dairy herd infections at the end of August, the state has now tallied 137 infected herds and at least 13 infected dairy farm workers. California, the country’s largest dairy producer, now has the most herd infections and human cases in the outbreak, which was first confirmed in March.

In the briefing Thursday, officials announced another front in the bird flu fight. A chicken farm in Washington state with about 800,000 birds became infected with a different strain of H5 bird flu than the one circulating among dairy farms. This strain likely came from wild birds. While the chickens on the infected farms were being culled, the virus spread to farmworkers. So far, two workers have been confirmed to be infected, and five others are presumed to be positive.

As of publication time, at least 31 humans have been confirmed infected with H5 bird flu this year.

With the spread of bird flu in dairies and the fall bird migration underway, the virus will continue to have opportunities to jump to mammals and gain access to people. Officials have also expressed anxiety as seasonal flu ramps up, given influenza’s penchant for swapping genetic fragments to generate new viral combinations. The reassortment and exposure to humans increases the risk of the virus adapting to spread from human to human and spark an outbreak.

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More unidentified illnesses linked to unexplained bird flu case in Missouri

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Unknowns —

The update raises questions about how the health investigation is going.

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A warning sign outside a laboratory testing the H5N1 bird flu virus at The Pirbright Institute in Woking, UK, on Monday, March 13, 2023.

Enlarge / A warning sign outside a laboratory testing the H5N1 bird flu virus at The Pirbright Institute in Woking, UK, on Monday, March 13, 2023.

More than a month after a person in Missouri mysteriously fell ill with H5-type bird flu, investigators in the state are still identifying people who became ill after contact with the patient, raising questions about the diligence of the ongoing health investigation.

On September 6, Missouri’s health department reported the state’s first human case of H5-type bird flu, one that appears closely related to the H5N1 bird flu currently causing a nationwide outbreak among dairy cows. But the infected person had no known contact with infected animals—unlike all of the other 13 human cases identified amid the dairy outbreak this year. Those previous cases have all occurred in dairy- or poultry-farm workers. In fact, Missouri has not reported bird flu in its dairy herds nor recent poultry outbreaks.

Given the unexplained source of infection, health investigators in the state have been working to track the virus both backward in time—to try to identify the source—and forward—to identify any potential onward spread. The bird flu patient was initially hospitalized on August 22 but recovered and had been released by the time the state publicly reported the case.

In an update Friday, September 27, the Centers for Disease Control and Prevention relayed that Missouri officials have now identified four more health care workers who experienced mild respiratory illnesses after caring for the person with bird flu. None of the four workers were tested for flu at the time of their illnesses and all have since recovered.

Testing new cases for antibodies to H5N1

The four newly identified cases bring the total number of health care workers who fell ill after contact to six. Missouri investigators had previously identified two other health care workers who developed mild respiratory symptoms. One of those workers was tested for flu around the time of their illness—and tested negative. But the other, like the four newly identified cases, was not tested. That person has since submitted a blood sample to test for bird flu antibodies, which would indicate a previous infection.

In addition, a household contact of the bird flu patient also fell ill at the same time as the patient, suggesting a possible common source of the infection.

The illnesses are concerning, given the fear that H5N1 bird flu could begin spreading from human to human and spark a widespread outbreak or even a pandemic. However, it can’t be overlooked that a plethora of other respiratory viruses are around—and SARS-CoV-2 transmission was relatively high in Missouri at the time—it’s impossible to draw any conclusions at this point about whether the illnesses were bird flu infections.

But, the illnesses do clearly raise concern about the health investigation, which is being conducted by Missouri officials. “The slow trickle of info is the most concerning part,” infectious disease expert Krutika Kuppalli wrote on social media Friday. The CDC can get involved at the request of a state, but such a request has not been made. For now, the CDC is only providing technical assistance from Atlanta.

In its update today, the CDC emphasized that “to date, only one case of influenza A(H5N1) has been detected in Missouri. No contacts of that case have tested positive for influenza A(H5N1).” The agency added that blood testing results for H5 antibodies are pending.

Currently, 239 dairy herds in 14 states have been infected with H5N1.

More unidentified illnesses linked to unexplained bird flu case in Missouri Read More »

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Person in Missouri caught H5 bird flu without animal contact

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Concerning —

The person recovered, and Missouri officials say risk to public is still low.

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The influenza virus from an image produced with transmission electron microscopy. Viral diameter ranges from around 80 to 120 nm.

Enlarge / The influenza virus from an image produced with transmission electron microscopy. Viral diameter ranges from around 80 to 120 nm.

A person in Missouri with no reported exposure to animals was confirmed to have been infected with H5-type bird flu, the Missouri Department of Health and Senior Services (MDHSS) announced late Friday.

MDHSS reported that the person, who has underlying medical conditions, was hospitalized on August 22 and tested positive for an influenza A virus. Further testing at the state’s public health laboratory indicated that the influenza A virus was an H5-type bird flu. The Centers for Disease Control and Prevention has now confirmed that finding and is carrying out further testing to determine if it is the H5N1 strain currently causing a widespread outbreak among US dairy cows.

It remains unclear if the person’s bird flu infection was the cause of the hospitalization or if the infection was discovered incidentally. The person has since recovered and was discharged from the hospital. In its announcement, MDHSS said no other information about the patient will be released to protect the person’s privacy.

The report marks the 15th human case of an H5-type bird flu infection in the country since 2022. But, the case stands out—and is quickly generating alarm online—because the man reported no contact with animals. All 14 of the previous cases occurred in farmworkers who had contact with either dairy cows or poultry that were known to be infected with H5N1.

The finding in a person without such an exposure raises the possibility that the H5N1 virus is spreading from person to person, undetected, or is spreading via an undetected animal source.

But, while the case raises concern, some infectious disease experts are cautious not to sound the alarm without more data on the case and potential exposures.

“[U]ntil such data is collected and analyzed, my level of alarm is only mildly heightened,” Caitlin Rivers, a senior scholar at the Johns Hopkins Center for Health Security and founding associate director of the Center for Forecasting and Outbreak Analytics at the CDC, said online.

“I am encouraged that this case was detected through existing surveillance systems, which bodes well for our ability to identify any additional cases in the future,” she added. “Federal, state, and local health officials maintained flu surveillance through the summer months in response to the H5 situation, and that was definitely the right move.”

But Rivers, like many of her colleagues, has long worried about H5N1’s potential to jump to humans and spark a pandemic.

To date, H5N1 is known to have infected 197 herds in 14 states. Missouri has not reported infected herds, but has reported infected poultry farms.

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