U.S. public health and clinical partners continue to monitor and respond to the global outbreak of highly pathogenic avian influenza A(H5N1). In November, the U.S. surpassed the previous record for number of birds affected, making this the worst domestic outbreak of avian influenza in poultry, with more than 58 million poultry affected in the U.S. to date. Thirteen human cases have been reported globally including one in the U.S., between January 2022 and June 1, 2023, of which six were hospitalized and two, tragically, died.
Currently, A(H5N1) is believed to pose a low risk to the health of the general public, however we know that influenza viruses are unpredictable, and the situation can change rapidly.
First, we remind partners that throughout the year, any samples that are run on a multi-respiratory panel that are influenza A positive, but did not return a valid subtype result, should be prioritized to ship to a public health laboratory immediately.
Second, given the severity of some recent human infections with A(H5N1) viruses, CDC recommends efforts to increase surveillance among people who are severely ill with respiratory disease during summer months when seasonal influenza incidence is very low. During these spring and summer months, CDC is asking that clinicians continue influenza testing for patients with respiratory illness and that hospitals and clinical laboratories ensure influenza A positive samples from ICU patients are subtyped either in the clinical laboratory or sent to state public health laboratory to identify cases of novel influenza (influenza A viruses that are not one of the currently circulating human subtypes). This would be in addition to standing recommendations that clinicians should always consider influenza testing, including subtyping, for patients with respiratory illness who are at higher risk for contracting novel influenza, such as those with a history of exposure to wild birds, poultry, or swine.
We believe these steps are important for continued surveillance of novel influenza in the U.S., including A(H5N1), as well as to efficiently detect variant influenza A cases, if they occur. As a reminder, human infection with any novel influenza A viruses is nationally notifiable and should be reported to CDC and state and local authorities.
CDC is encouraging this increase in testing in the summer when influenza testing may not be as routine as it is during the fall and winter months, and because of the critical importance of early identification of any influenza A(H5N1) cases that may occur. We expect this request to be manageable in the summer because of the relatively lower levels of respiratory illness and anticipated low levels of influenza positive tests.
We appreciate your partnership in ensuring that human cases of novel influenza in the U.S. are identified and contained immediately. Thank you for your continued support in this effort and the prevention and control of influenza. Please visit H5N1 Bird Flu: Current Situation Summary | Avian Influenza (Flu) (cdc.gov) for the most up-to-date information.
For additional guidance on testing, specimen collection, transport, and handling instructions, please contact your local public health officials or the state public health laboratory at 800-821-7284.