The Centers for Disease Control (CDC) has confirmed a person in the United States tested positive for highly pathogenic avian influenza (flu, HPAI) H5N1 virus on April 1, 2024.1,2 The patient had contact with dairy cattle believed to be infected with the virus and reported symptoms consistent with conjunctivitis.1 While the CDC notes that the current public health risk remains low, the organization is watching the situation carefully and working with states to monitor individuals who have been exposed to certain animals.2 The CDC recommends those with prolonged or unprotected exposure to infected birds, animals, or livestock observe proper safety and preventative measures to avoid contracting the H5N1 virus.1 Notably, human to human spread is not a concern for this virus, according to the CDC.2
H5N1 bird flu primarily infects birds, but some strains can infect humans with prolonged, unprotected exposure to infected birds, animals, and livestock. While uncommon, this is the second reported case of H5N1, with a previous case in Colorado in 2022.1,2 Symptoms of H5N1 bird flu range from mild upper respiratory symptoms or eye infection to severe cases, such as pneumonia.1 The CDC recommends people with exposure to the virus, including those wearing personal protective equipment, monitor for signs of illness for 10 days after the exposure event.1
Currently, flu antiviral medications are considered the most effective treatment against H5N1, with analyses showing no significant changes that would render them resistant to these medications.1 The CDC noted that the recent human case was found to be susceptible to flu antiviral drugs.2 However, the CDC stated that it is important to note that seasonal flu vaccines will not protect against H5N1.1 However, prior examinations show that candidate vaccine viruses developed to fight clade 2.3.4.4b viruses may offer protection against H5N1 viruses.1
In March 2024, the United States Department of Agriculture (USDA) released multiple reports of infected animals in 3 states.1 HPAI was detected in dairy cows in Texas and Kansas through testing of unpasteurized milk and throat swabs from sick cattle.1,2 The samples tested positive for HPAI A(H5) virus of the genetic clad 2.3.4.4b, which is widespread among wild birds globally.1 Further tests conducted by the USDA’s National Veterinary Services Laboratory confirmed a Michigan herd from Texas tested positive as well.1
Key Takeaways
- Risk Factors and Symptoms: The H5N1 bird flu primarily infects birds but can infect humans with prolonged exposure to infected animals. Symptoms can range from mild upper respiratory symptoms or eye infection to severe cases like pneumonia. The CDC advises individuals with prolonged exposure to infected birds, animals, or livestock to monitor for signs of illness for 10 days after exposure.
- Preventative Measures and Treatment: The CDC recommends avoiding contact with sick or dead animals suspected of H5N1 infection and refraining from consuming undercooked or uncooked animal products from infected animals. Although seasonal flu vaccines do not protect against H5N1, there are candidate vaccine viruses being developed to combat certain strains of the virus. Antiviral medications are currently considered the most effective treatment against H5N1, with no significant changes noted to render them ineffective against the virus.
- Public Health Response and Monitoring: The CDC is closely monitoring the situation in collaboration with other agencies like the USDA and FDA. They are investigating people exposed to H5N1 viruses and stress the importance of readiness and surveillance due to the constant evolution of flu viruses. Despite the confirmed case, the CDC maintains that the risk to the general public remains low but encourages vigilance and adherence to safety measures.
Individuals are strongly advised to avoid contact with sick or dead animals confirmed or suspected to have the H5N1 virus infection, according to the CDC.1,2 This includes animal byproducts like unpasteurized milk, feces, materials contaminated by infected animals, or animal carcasses. The CDC also recommends individuals not consume undercooked or uncooked animal products, such as poultry meat and unpasteurized dairy products from animals with bird flu.1 However, both the FDA and USDA assure there is no significant safety threat to commercial milk and dairy products due to interstate commerce pasteurization requirements. Pasteurization is proven to eliminate bacteria and viruses, reducing the risk of consuming contaminated animal products. Furthermore, regulations prohibit milk from infected animals be processed for human consumption.1
The CDC additionally noted that the organization is working closely with the USDA, FDA, state health departments, and local authorities to monitor and investigate people exposed to H5N1 viruses.1 According to the CDC, flu viruses are constantly changing, which means readiness and surveillance efforts are critical.1,2 Further, despite this confirmed case of H5N1, the CDC considers the risk to public health to be low.1
“This is a developing situation, and CDC will share additional updates as new relevant information becomes available,” the CDC wrote in a statement.1 Overall, the CDC highlighted in the statement the importance of vigilance, preventive measures, and coordinated efforts among public health agencies to manage and respond to this case of the H5N1 bird flu.1,2
Regular updates on H5N1 bird flu cases can be found through the USDA Animal and Plant Health Inspection Service.
References
CDC. Highly Pathogenic Avian Influenza A (H5N1) Virus Infection Reported in a Person in the U.S. April 1, 2023. Accessed April 16, 2024. https://www.cdc.gov/media/releases/2024/p0401-avian-flu.html
CDC. H5N1 Bird Flu: Current Situation Summary. CDC.gov. Updated April 22, 2024. Accessed April 23, 2024. https://www.cdc.gov/flu/avianflu/avian-flu-summary.htm
