In April 2024 the United States reported a case of human infection with an influenza A(H5N1) virus; on 9th April 2024 the WHO shared a “disease outbreak news” update on the situation, assessing the public health risk to the general population as “low”. This follows a CDC press release, which emphasises that the agency is working “closely” with state and federal agencies to “further investigate and closely monitor this situation”.
WHO is notified of a case
On 1st April 2024, the IHR NFP of the US notified WHO of a laboratory-confirmed human case of avian influenza A(H5N1), which was detected in the state of Texas. The case is an adult who had a history of exposure to cows through work at a commercial dairy cattle farm and presented with conjunctivitis on 27th March. On 28th March, respiratory and conjunctival specimens were collected from the case and tested by the Texas Tech University Bioterrorism Response Laboratory.
RT-PCR analysis revealed that both specimens were “presumptive positive” for influenza A(H5) virus; the specimens were passed on to the US CDC for further testing, which confirmed them as high pathogenicity avian influenza (HPAI) A(H5N1) virus clade 2.3.4.4b. The patient was advised to isolate and has been treated with antiviral treatment in accordance with US CDC guidance; WHO states that the individual “was recovering” at time of reporting.
Cases in cattle
WHO reflects that influenza A virus infection is “exceptionally rare” in bovine species. However, the human case had exposure to dairy cattle, presumed to be infected with HPAI A(H5N1). This follows a report from the USDA on 25th March that HPAI A(H5N1) virus had been detected in dairy cattle and unpasteurised milk samples from cattle in Texas and Kansas in four herds.
Additional detections have since been reported in six states: Idaho, Kansas, Michigan, New Mexico, Ohio, and Texas. WHO understands that USDA continues to monitor and test samples from other farms where cattle are “displaying decreased lactation, low appetite, and other signs”.
Public health response and risk assessment
The following public health measures have been implemented:
- Surveillance activities are being conducted in Texas.
- US CDC is working with state health departments to monitor workers who may have been in contact with infected or potentially infected birds/animals.
- US CDC has issued public recommendations.
“The United States has a robust surveillance system that is designed to mitigate the spread of animal diseases, thereby protecting public health, and maintaining a safe food supply for domestic and international markets.”
As the virus has not acquired mutations that facilitate transmission among humans, WHO considers “available information” to conclude that the public health risk to the general population is “low”. For occupationally exposed persons the risk of infection is considered “low-to-moderate”.
Dr Cohen at the Congress
We were privileged to hear from US CDC Director Dr Mandy Cohen during the Congress in Washington this April, during which she emphasised to MedPageToday that her agency is “all over” the threat of avian influenza. In her keynote speech she highlighted the importance of intelligent investment to tackle this and other growing issues.
“We need to continue to invest in data, in lab capacity, in our ability to respond to health threats, and we need a talented workforce.”
Dr Cohen reflected that “we cannot solve problems we don’t see”, addressing the strengths and potential for growth of the US disease surveillance capabilities.
It was fantastic to hear an almost immediate reaction from Dr Cohen to the threat of avian influenza at the Congress last week, and we will continue to track the developments of this and other infectious diseases here; do subscribe for more updates.
