The United States CDC confirmed in September 2024 that a human case of avian influenza A(H5) has been reported by the state of Missouri. The case was identified through seasonal flu surveillance and an investigation into the potential exposure is underway at the Missouri Department of Health and Senior Services (DHSS). The patient was hospitalised but has been discharged and has made a recovery. This is the 14th human case of H5 reported in the United States in 2024 but the first without a known occupational exposure to sick or infected animals.
The case
Missouri DHSS states that this case was identified through “ongoing influenza surveillance”. The Missouri State Public Health Laboratory received specimen taken from a patient who was hospitalised on 22nd August. The patient has underlying medical conditions and tested positive for influenza A. The laboratory conducted further testing to determine the influenza subtype, which resulted in “presumptive detection of the H5 subtype”. The specimen was then sent to CDC for additional testing, when H5 subtype was confirmed. The patient has recovered and returned home. Notably, this is the first case of H5 without a known occupational exposure to sick or infected animal. No H5 outbreaks in cattle have been reported in Missouri, but H5 outbreaks have been reported in commercial and backyard poultry flocks.
CDC risk assessment
CDC continues to describe the risk to the public from H5N1 as “low”, and recommendations have not changed. However, the agency recognises that “circumstances may change quickly” as information emerges.
“The results of this investigation will be particularly important in light of the current lack of an obvious animal exposure.”
More questions arise
As the available information on this case is limited, public health experts have urged a step up in surveillance and public health communication. Professor Marion Koopmans, head of the Erasmus Medical Centre Department of Viroscience, told STAT that a “better safe than sorry” investigation would be encouraging.
“I would want to see a wide net cast here… [this would] not have to be all in the public eye, but I would want to know this is [being] taken up very seriously.”
Another expert, University of Saskatchewan’s emerging infectious disease specialist Dr Angela Rasmussen, was unimpressed with the delay in reporting the case.
“The choice to drag their feet and give no details about follow up is mystifying and reflects very poorly on both Missouri state and federal epidemic response capacity and practice.”
Dr Rasmussen tweeted that “this is being presented like it’s a triumph for flu surveillance” but finds it “pretty unbelievable” that there’s “no information about how the case is being investigated”.
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