Human Avian Influenza A(H5) Virus: CDC Statement



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The CDC released the following statement on Thursday, April 28, 2022:

One person has tested positive for the avian influenza A(H5) virus (H5 bird flu) in the United States, as reported by Colorado and confirmed by the CDC. This case occurred in a person who had direct exposure to poultry and was involved in the culling (depopulation) of poultry suspected of having H5N1 avian influenza. The patient reported fatigue for a few days as the only symptom and has since recovered. The patient is isolated and treated with oseltamivir, an antiviral flu drug. Although it is possible that the detection of H5 avian influenza in this sample was the result of surface contamination of the nasal membrane, this cannot be determined at this time and the positive test result meets the criteria for an H5 case. The appropriate public health response at this time is to assume it is an infection and take steps to contain and treat it.

Avian flu H5N1/CDC

This case does not change the human risk assessment for the general public, which the CDC considers low. However, people who have occupational or recreational exposures to infected birds are at higher risk of infection should take appropriate precautions outlined in CDC guidelines.

The CDC has been monitoring illness in people exposed to birds infected with the H5N1 virus since these outbreaks were detected in wild birds and poultry in the United States in late 2021 and through 2022. To date, H5N1 viruses have been found in US commercial and backyard birds in 29 states. and in wild birds in 34 states. The CDC has tracked the health of more than 2,500 people exposed to birds infected with the H5N1 virus and this is the only case that has been found so far. Others involved in the culling operation in Colorado have tested negative for H5 virus infection, but are being retested out of an abundance of caution.

This is the second human case associated with this specific group of currently predominant H5 viruses, and the first case in the United States. The first case internationally occurred in December 2021 in the UK in a person who had no symptoms and kept birds infected with the H5N1 virus. Over 880 human infections with earlier H5N1 viruses have been reported since 2003 worldwide, however, the predominant H5N1 viruses currently circulating among birds globally are different from earlier H5N1 viruses.

Infected birds excrete the H5N1 virus in their saliva, mucous membranes and feces. H5N1 virus infections in people are rare; however, human infections can occur when enough virus enters a person’s eyes, nose, or mouth, or is inhaled. People who have close or prolonged unprotected contact (not wearing respiratory or eye protection) with infected birds or places that sick birds or their mucous membranes, saliva or feces have touched may be at greater risk of infection by the H5N1 virus. In people with avian influenza virus infections, illnesses range from mild (eg, eye infection, upper respiratory tract symptoms) to severe illness (eg, pneumonia) that can lead to dead. The only previous human case associated with this group of H5N1 viruses produced no symptoms. Spread of past H5N1 viruses from an infected person to a close contact in the past has occurred very rarely and has not led to sustained human-to-human spread.

Local, state and federal health partners are working together to prevent the spread of this H5N1 virus among birds and humans. The United States Department of the Interior and the United States Department of Agriculture (USDA) are the primary federal departments for the investigation and control of outbreaks of avian influenza in wild birds, and the Animal Health Inspection Service USDA Plant and Plant Protection Agency is the agency responsible for these activities in domesticated birds such as poultry. . The US Department of Health and Human Services and the CDC are the primary federal public health partners for this situation.

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This single H5 positive human case does not change the human health risk assessment. The CDC will continue to monitor this situation closely for signs that the risk to human health has changed. Signals that could increase public health risk could include multiple reports of H5N1 virus infections in people exposed to birds, or identification of spread from an infected person to a close contact. The CDC also monitors H5N1 viruses for genetic changes that have been associated with mammalian adaptation, which could indicate that the virus is adapting to spread more easily from birds to humans. The CDC is taking routine preparedness and prevention measures, which include an existing candidate vaccine virus that could be used to make a vaccine for people if needed.

The CDC has guidance for clinicians, public health practitioners, and people potentially exposed to birds. As a reminder, people should avoid contact with poultry that appear sick or dead and if possible avoid contact with surfaces that appear contaminated with the droppings of wild or domestic birds. If you must handle sick or dead wild birds or poultry, minimize direct contact by wearing gloves and washing your hands with soap and water after touching birds. If possible, wear respiratory protection such as a medical mask and eye protection such as goggles. Properly handled and cooked poultry and poultry products are safe to eat in the United States. Proper handling and cooking of poultry and eggs to an internal temperature of 165°F kills bacteria and viruses, including H5N1 viruses. Additional information on protective measures around birds, including what to do if you find a dead bird, is available. The CDC also has guidance for specific groups of people exposed to poultry, including poultry workers and people responding to poultry outbreaks. The CDC will continue to provide further updates on the situation and update guidance as needed.