Austin, Texas – The discovery of two human cases of Influenza A(H5) virus infection has raised concerns among health officials in the United States. On April 1, 2024, the Texas Department of State Health Services confirmed the first case after a commercial dairy farm worker tested positive for highly pathogenic avian influenza (HPAI) A(H5N1) virus. Following this, a second case was reported on May 22, 2024, in Michigan, presenting a potential cow-to-human transmission of the virus. These incidents mark the first known instances of presumed transmission of an avian influenza A virus from cows to humans.
The cases originated from dairy cattle herds in various states, showcasing signs of infection such as decreased milk production, nasal discharge, and alterations in milk consistency. The infected dairy cows were identified in 52 herds across Colorado, Idaho, Kansas, Michigan, and other states. Furthermore, laboratory findings confirmed the presence of A(H5N1) viruses in barn cats, birds, and other animals within the vicinity of affected farms.
Globally, from 1997 to late April 2024, a total of 909 sporadic human cases of A(H5N1) were reported, with a fatality rate of 52%. The continuous surveillance effort aimed at monitoring persons exposed to infected animals has been ongoing since the first detection of HPAI A(H5) viruses in North America in 2014. To combat the spread of the virus, health authorities have implemented a wide range of response activities, including monitoring infections, conducting research on virus pathogenesis, and developing novel influenza A candidate vaccine viruses for pandemic preparedness.
As part of the response plan, healthcare providers have been advised to administer antiviral treatments promptly to patients with confirmed or suspected A(H5N1) infection. Additionally, efforts are being made to increase awareness about the virus among healthcare providers and the public to ensure early detection and effective management of cases. The National Institute of Allergy and Infectious Diseases (NIAID) is also actively exploring various treatment options, including direct-acting antiviral medications and monoclonal antibodies, to combat the virus effectively.
Moving forward, epidemiological investigations are being planned to assess the risk posed by these occurrences. Collaborative efforts between states, affected farms, and health and agricultural partners will be crucial in conducting in-depth studies to shed more light on the transmission dynamics of the virus. This comprehensive approach underscores the urgency of addressing the threat posed by the transmission of avian influenza A viruses to human populations, highlighting the need for proactive measures to safeguard public health.