Novel Avian Influenza A
(H5N1, H5N2, H7N3, and H7N9)

New (novel) avian influenza A viruses have the potential to cause a pandemic if the virus were to change to become easily and sustainably spread from person-to-person.

Background

What is a novel avian influenza A virus?

New (novel) avian influenza A viruses are influenza viruses that are new to humans, meaning that very few people will have immunity and a vaccine might not be widely available.

Where do novel avian influenza A viruses come from?

Novel avian influenza A viruses can come from animal influenza viruses and can change to gain the ability to infect people easily and spread person-to-person. Wild aquatic birds, like loons, and wild waterfowl, such as ducks or geese, are considered reservoirs for avian influenza A viruses. Influenza A viruses are constantly changing, which can lead to novel avian influenza A viruses circulating in domestic poultry or other animals that can place people at risk.

How sick can people get if they get infected with a novel avian influenza A virus?

How sick people get will depend on the characteristics of the virus, whether or not people have any immunity to that virus, and the health and age of the person being infected.

What is an influenza pandemic?

An influenza pandemic is a global outbreak of a new influenza virus that is very different from current and recently circulating human seasonal influenza viruses. It is possible, on very rare occasions, for non-human influenza A viruses to change to infect people more easily and spread efficiently from person-to-person. Novel avian influenza A viruses have the potential to cause a pandemic if the virus were to change to become easily and sustainably spread from person-to-person.

How do we prevent novel avian influenza A infections and pandemics?

Global influenza surveillance is the foundation of influenza preparedness and response for influenza viruses. Since influenza A can cause disease ranging from mild to severe including death, public health workers closely watch trends in infections and follow-up on occupational exposures to avian influenza A in populations that have close contact with infected animals (such as poultry workers). By closely monitoring exposures to animal influenza viruses, people can be treated faster to help prevent the spread of infection and the development of severe disease.

Viruses of Special Concern:
Highly Pathogenic Avian Influenza (HPAI)

Human infections with novel avian influenza virus are concerning because flu changes rapidly and animal flu viruses can change such that they may gain the ability to infect people easily and spread among people.

How is HPAI spread?

• Avian influenza viruses are spread through direct contact with infected birds or animals, as well as through contact with contaminated items such as bedding, feed or water.

Can humans be infected with HPAI?

• Some highly pathogenic avian flu viruses can infect people causing mild to severe respiratory illness.
• Symptoms in infected people can include influenza-like illness (e.g., fever with cough and/or sore throat) and red, itchy eyes. Less common signs and symptoms include diarrhea, nausea, vomiting, or seizures.
• Person-to-person transmission of avian influenza viruses is very rare.
• HPAI does not pose a health risk to the public. Only persons who have direct contact with infected birds or other animals are potentially at risk.
  • Avian influenza A(H5N1) is primarily an occupational hazard that impacts workers in the poultry and dairy industries.
  • People in contact with infected birds or other animals should be monitored by public health to make sure they don't become sick. 
  • In some situations, individuals may be recommended to take antiviral medication as a precaution.
  • As part of the current H5N1 response, CDC has asked state health departments to make personal protective equipment (PPE) available for a one-time distribution to workers in industries who may have exposure to influenza A(H5N1). Read the full letter to workers in the dairy, poultry, milk processing, poultry and beef slaughter industries and learn how to request your PPE.
    • May 17, 2024, Letter to workers in the dairy, poultry, milk processing, poultry and beef slaughter industries (PDF)
• Please consider seasonal influenza vaccination if you have not yet received it this season (since August of 2023). While the seasonal influenza vaccine will not prevent avian strains of influenza, it can prevent illness due to seasonal influenza strains, which are still circulating.
  • Find where to get vaccinated with the vaccination finder: Where to Get Vaccinated

More information on avian influenza A subtypes is available at CDC: Avian Influenza (Bird Flu)