Interim Guidance on Influenza Antiviral Post-exposure Prophylaxis of Persons Exposed to Birds or Other Animals with Novel Influenza A Viruses Associated with Severe Human Disease or with the Potential to Cause Severe Human Disease

Background

Examples of novel influenza A viruses with the potential to cause severe human disease can be found on Bird Flu Virus Infections in Humans, including highly pathogenic avian influenza A(H5N1) and A(H5N6) viruses, and avian influenza A(H7N9) virus. A novel influenza A virus is considered to have the potential to cause severe human disease if previous cases of infection with the same hemagglutinin subtype [e.g., HPAI A(H5) or A(H7) viruses] have been associated with severe human disease or in the setting of recent human infections with novel influenza A virus subtypes for which limited data on disease severity are available. Additionally, more information about specific novel influenza A viruses and past reported human infections with novel influenza A viruses is available. There is limited experience with these newly detected viruses to inform public health guidance regarding use of antiviral chemoprophylaxis. However, these viruses are thought to have the potential to infect people and cause severe illness. Rare human infections with novel influenza A viruses have been documented in the U.S. since 2002. CDC will update this guidance as additional information becomes available.

Exposure to Birds or Other Animals Infected with Novel Influenza A Viruses

Persons with recent exposure (within 10 days) to novel influenza A viruses include exposure to A(H5) or A(H7) virus-infected animals.

Close exposure is defined as being within approximately 6 feet of birds or other animals with confirmed novel influenza A virus infection by A(H5) or A(H7) viruses. The risk of infection with novel influenza A viruses is higher in people with unprotected exposures (e.g., not using recommended respiratory and eye protection) than in those who used such protective equipment.

Bird or other animal exposures can include, but are not limited to:

Exposure to Birds or Other Animals with Unknown Novel Influenza A Virus Infection Status

More information on persons with unprotected exposure (e.g., not using respiratory and eye protection) can be found here: Case Definitions for Investigations of Human Infection with Avian Influenza A Viruses in the United States.

It is not possible to know whether well-appearing, sick or dead wild birds or other animals are infected with novel influenza A viruses until they are tested. More information can be found at:

Monitoring of Exposed Persons

Exposed persons should monitor themselves daily for signs and symptoms of new illness for 10 days after the last known exposure. Signs and symptoms may include fever (temperature of 100ºF [37.8ºC] or greater) or feeling feverish, cough, sore throat, runny or stuffy nose, muscle or body aches, headaches, fatigue, eye redness (or conjunctivitis), shortness of breath or difficulty breathing. Fever may not always be present. Less common signs and symptoms are diarrhea, nausea, vomiting, or seizures.

Any exposed person who develops any new illness symptoms such as those listed above, and particularly any new respiratory symptoms (e.g., cough, sore throat, shortness of breath, difficulty breathing), conjunctivitis, or other symptoms, with or without fever (see clinical criteria) should be promptly tested for novel influenza A virus infection.

Post-exposure Chemoprophylaxis of Exposed Persons

Post-exposure prophylaxis (PEP) with influenza antiviral medications can be considered for exposed persons. Decisions to initiate post-exposure antiviral chemoprophylaxis should be based on clinical judgment, with consideration given to the type of exposure (e.g. without use of respiratory and eye protection), duration of exposure, time since exposure (e.g. less than 2 days), known infection status of the birds or other animals the person was exposed to, and whether the exposed person is at higher risk for complications from seasonal influenza.

• If PEP is initiated, antiviral post-exposure prophylaxis should begin as soon as possible (ideally within 48 hours) after the first exposure.
• Oral oseltamivir at treatment dosing frequency (one dose twice daily) is recommended instead of the typical antiviral chemoprophylaxis regimen (once daily) for seasonal influenza. All human infections with highly pathogenic avian influenza A(H5N1) virus in the U.S. have been with viruses susceptible to oseltamivir.
• Antiviral post-exposure prophylaxis with oseltamivir (twice daily) should be continued for 5 or 10 days. If the exposure was time-limited and not ongoing, the recommended duration is 5 days from the last known exposure. If the exposure is likely to be ongoing, a duration of 10 days is recommended because of the potential for prolonged infectiousness from the infected animal(s).
• Specific dosage recommendations for treatment by age group are available at Recommended Dosage and Duration of Influenza Antiviral.
• This recommendation for oral oseltamivir with twice daily antiviral post-exposure prophylaxis dosing is based on limited data in animals that support higher chemoprophylaxis dosing for avian influenza A(H5N1) virus infection 1, and on the desire to reduce the potential for development of antiviral resistance while receiving once daily chemoprophylaxis if infection occurred 234.
• To support post-exposure prophylaxis with oseltamivir using twice daily dosing for novel influenza A viruses associated with severe human disease, including highly pathogenic avian influenza A(H5N1) virus, CDC issued Emergency Use Instructions (EUI) for oseltamivir.

Chemoprophylaxis is not routinely recommended for personnel involved in culling non-infected or likely non-infected bird populations. Chemoprophylaxis is also not recommended as a control measure for personnel involved in handling sick birds or decontaminating affected environments (including animal disposal) who used proper personal protective equipment.