The United States has reported its first case of avian influenza A(H5) virus (H5 bird flu) with a person in Colorado who was confirmed to have contracted the virus.
The person had direct exposure to poultry and was involved in the culling of poultry with presumptive H5N1 bird flu.
According to the Centers for Disease Control and Prevention, which reported the case on April 28, the patient reported fatigue for a few days as their only symptom and has since recovered.
This is the second human case associated with this specific group of H5 viruses that are currently predominant, and the first case in the United States.
In a media statement, the CDC said it has been monitoring for illness among people exposed to H5N1 virus-infected birds since these outbreaks were detected in U.S. wild birds and poultry in late 2021 and into 2022.
So far, H5N1 viruses have been found in U.S. commercial and backyard birds in 29 statesexternal icon and in wild birds in 34 states. CDC has tracked the health of more than 2,500 people with exposures to H5N1 virus-infected birds and this is the only case that has been found to date. Other people involved in the culling operation in Colorado have tested negative for H5 virus infection, but they are being retested out of an abundance of caution.
Records show that the firstexternal icon case internationally occurred in December 2021 in the United Kingdom in a person who did not have any symptoms and who raised birds that became infected with the H5N1 virus.
More than 880 human infections with earlier H5N1 viruses have been reported since 2003 worldwide, however, the predominant H5N1 viruses now circulating among birds globally are different from earlier H5N1 viruses, the CDC said.
Infected birds shed H5N1 viruses in their saliva, mucous, and feces. H5N1 virus infections among people are rare; however, human infections can happen when enough virus gets into a person’s eyes, nose, or mouth, or is inhaled.
The patient diagnosed with the bird flu virus in the U.S. is being isolated and treated with the influenza antiviral drug oseltamivir. While it is possible the detection of H5 bird flu in this specimen is a result of surface contamination of the nasal membrane, that can’t be determined at this point and the positive test result meets the criteria for an H5 case.
This case does not change the human risk assessment for the general public, which CDC considers to be low. However, people who have job-related or recreational exposures to infected birds and are at higher risk of infection should take appropriate precautions outlined in CDC guidance, the Centers said.
