The CDC has verified a second case of human H5 bird flu in Michigan, with the third case linked to the dairy outbreak.
As of May 30, 2024, a second individual in Michigan has been diagnosed with highly pathogenic avian influenza (HPAI) A(H5) virus infection. This marks the third human case linked to an ongoing outbreak of A(H5N1) in dairy cows across multiple states. None of the three cases are connected to each other. Similar to the previous instances in Texas and Michigan, the affected individual works on a dairy farm and had contact with infected cows, indicating a likely transmission from cows to humans.
This case is the first in the United States to exhibit typical symptoms of acute respiratory illness associated with influenza virus infection, including A(H5N1) viruses. The Centers for Disease Control and Prevention (CDC) continues to monitor data from influenza surveillance systems, particularly in affected states, and has not observed any unusual influenza activity among the general population, such as an increase in emergency room visits or laboratory-confirmed cases.
At present, this case does not alter CDC's current assessment of the human health risk posed by A(H5N1) bird flu to the general public in the U.S. as all three isolated cases had direct contact with infected cows. The risk is dependent on exposure, with direct contact with infected animals being the primary concern in this situation. The risk to individuals without exposure to infected animals remains low. Nevertheless, this development highlights the importance of following recommended precautions for individuals with exposure to infected or potentially infected animals. Those who have had close or prolonged, unprotected contact with infected birds, livestock, or environments contaminated by infected animals are at a higher risk of infection and should take necessary precautions.
Background of the Case:
A dairy worker who had contact with H5N1-infected cows at a different farm than the previous case has reported symptoms to local health officials. The symptoms include upper respiratory tract symptoms such as cough without fever, as well as eye discomfort with watery discharge. The patient has been given antiviral treatment with oseltamivir and is currently isolating at home. Fortunately, their symptoms are improving. The patient's household contacts have not shown any symptoms so far, but they are being closely monitored for any signs of illness. They have also been offered oseltamivir as a precautionary measure. Other workers at the same farm have not reported any symptoms, but all staff members are being monitored. At this time, there is no evidence of person-to-person transmission of A(H5N1) viruses.
Specimens were collected from the patient, and one of them tested positive for influenza A(H5) virus at the state health department laboratory using the CDC test. These specimens have been sent to the CDC for further testing. The CDC received the specimens on May 29, and the testing results confirmed the infection with A(H5) virus on the same night. Michigan has been informed about these results.
The genetic sequencing to determine the neuraminidase designation of the influenza virus (the N in the subtype) is currently pending at the CDC. The results of this sequencing will be available within 1-2 days if successful. Additionally, further genetic analysis will be conducted to identify any changes in the virus that could impact the agency's risk assessment.
CDC Activities and Risk Assessment
This particular case was identified as part of Michigan's active monitoring program for individuals who have been exposed to infected livestock. The collaboration between Michigan and CDC has been instrumental in detecting this case. The discovery of an additional H5 case is not unexpected and highlights the importance of a proactive approach to public health. Considering the widespread presence of the virus in dairy cows, it would not be surprising to see more cases in individuals with higher risk exposures. Currently, one of CDC's top priorities is to prevent further A(H5N1) infections among dairy herd workers, who face a greater risk of exposure. To address this, CDC has previously issued updated interim recommendations for worker protection, specifically for those working with dairy cows, and has urged states to provide personal protective equipment to farmworkers. Additionally, the agency is actively engaging with organizations representing farmworkers through ongoing outreach efforts.
CDC Recommendations
It is advised that individuals wear the appropriate personal protective equipment when coming into contact with infected or potentially infected animals. Furthermore, they should closely monitor their health for a period of 10 days following their most recent exposure. For more detailed information on CDC's recommendations regarding worker protection and the use of personal protective equipment (PPE), please refer to their guidelines.
In order to minimize the risk of infection, people should avoid close, prolonged, or unprotected contact with sick or deceased animals, including wild birds, poultry, other domesticated birds, and both wild and domesticated animals such as cows.
Additionally, individuals should refrain from unprotected contact with animal feces, bedding (litter), unpasteurized ("raw") milk, or any materials that have come into contact with birds or other animals suspected or confirmed to carry the A(H5N1) virus.