Avian Influenza Quick Facts
Current as of June 21, 2024
This document provides health care providers and emergency planners with resource links to improve their readiness forpotential human infections with avian influenza A viruses. Users should refer to the websites of the U.S. Department ofAgriculture’s Animal and Plant Health Inspection Service (APHIS), the Centers for Disease Control and Prevention (CDC), theFood and Agriculture Organization of the United Nations (FAO), and the World Health Organization (WHO) for the most upto-date information.
What is avian influenza?
Avian influenza refers to the disease caused by infection with avian influenza Type Aviruses. These viruses naturally spread among wild aquatic birds worldwide and can
infect domestic poultry and other bird and animal species.

APHIS: Avian Influenza
CDC: Avian Influenza (Bird Flu)
WHO: Influenza (Avian and OtherZoonotic)

Where is avian influenza found?
Avian influenza A viruses are found throughout the world. FAO’s Emergency Prevention
System for Animal Health publishes periodic situation updates tracking avian influenza
outbreaks in animals that include global distribution maps and details about the type ofvirus, date and location found, the affected species, and number of events. Thesesituation updates also track human infections. APHIS’ avian influenza surveillance
program reports on detections in the U.S. of avian influenza in wild birds,
commercial/backyard flocks, livestock, and wild mammals.
Why is avian influenza of interest to health care and public health professionals?
Avian influenza A viruses do not normally infect humans. However, sporadic humaninfections with avian influenza A viruses have occurred, including two cases in theUnited States. Health care providers, public health professionals, and emergency
managers monitor avian influenza A activity to better detect rare human cases in areas
where animal outbreaks are occurring and to prepare for a potential pandemic that mayoccur if these viruses gain the ability to spread easily from person-to-person.

APHIS: Detections of Highly Pathogenic
Avian Influenza
CDC: Highlights in the History of Avian
Influenza Timeline
FAO: Global Avian Influenza Viruses withZoonotic Potential Situation Update
FAO: Avian Influenza A(H7N9) VirusSituation Update

CDC: Monitoring for Influenza Viruses
WHO: Influenza at the Human-Animal
Interface Summary and Assessment

How are avian influenza A virus risks assessed?
CDC’s Influenza Risk Assessment Tool assesses and classifies 24 novel influenza A viruses
according to low, moderate, and high risk. WHO developed the Tool for Influenza
Pandemic Risk Assessment to similarly assess the risk of influenza viruses withpandemic potential. These tools are intended to assess the pandemic potential of eachvirus; they cannot predict an influenza pandemic.

CDC: Influenza Risk Assessment Tool (IRAT)
WHO: Tool for Influenza Pandemic Risk
Assessment (TIPRA)

Which avian influenza A viruses are of greatest interest?
Several avian influenza A viruses are of particular concern due to their known ability toinfect humans. While there has been limited, non-sustained human-to-humantransmission of some avian influenza A viruses reported, none of the viruses currently
circulating among birds or other animals appear to have acquired the ability to do soeasily or in a sustained manner. Most human infections result from direct humancontact with infected animals or contaminated environments. WHO publishes weekly
avian influenza situation reports to describe newly reported cases. Viruses of concern asof May 3, 2024, include:••••

ASPR: ASPR’s Response to H5N1 Bird Flu
CDC: H5N1 Bird Flu: Current Situation
WHO: Surveillance-Avian Influenza-WesternPacific

H5N1: 889 human cases and 463 deaths in 23 countries since 2003
H7N9: 1,568 human infections confirmed (in China plus one imported case in Malaysia and two imported cases in Canada)
since 2013, with 616 deaths. No human cases have been reported since March 2019.
H5N6: 90 human cases and 35 deaths in China and Laos
H9N2: 101 human cases and 2 deaths in China, Cambodia, and Vietnam

Limited cases of avian influenza H3N8, H5N2, H5N8, H6N1, H7N2, H7N3, H7N4, H7N7, H10N3, H10N5, H10N7, and H10N8 have also beenreported in humans.

What makes avian influenza A virus infections different from seasonal influenza A and B viruses?
Human seasonal influenza Type A (subtypes H1 and H3) and B viruses circulate yearround among people worldwide and cause epidemics every year, often peaking between December and February in the U.S. With ongoing virus circulation, mostindividuals have some immunity from exposures to seasonal influenza A and B viruses
from previous years or from seasonal influenza vaccination. However, some
populations – including those 65 and older, those 5 and younger, pregnant people, andindividuals with certain chronic health conditions – are at increased risk for serious
illness from seasonal influenza, possibly leading to hospitalization or death. In contrast,avian influenza A virus infection in humans is rare and is mostly limited to those whohave close contact with infected animals or environments contaminated by them. Even
healthy individuals infected with avian influenza A could be at risk for serious illness ordeath. Seasonal influenza vaccines protect against select human seasonal influenza A
and B viruses and do not protect humans from avian influenza A viruses.

CDC: About Flu
CDC: What Causes Bird Flu Virus Infectionsin Humans

How are human cases of avian influenza identified and treated?
Most patients with influenza-like illness are likely to be infected with a seasonal influenza
virus or other common respiratory virus. Clinicians should consider avian influenza A
virus infection in patients with signs and symptoms of acute or lower respiratory tract
CDC: Case Definitions for Investigations ofinfection or conjunctivitis or complications of acute respiratory illness without an
Human Infection with Avian Influenza A
identified cause and who have been exposed to animals infected with avian influenza
Viruses in the United States
A(H5), A (H7) or A(H9) viruses or environments contaminated by them, had close contact CDC: Clinical Overview of Evaluating andwith someone known or suspected to be infected with avian influenza A virus, or had
Managing Patients Exposed to Birds
unprotected exposure to live avian influenza A virus in a laboratory. If a clinician suspects Infected with Avian Influenza A Viruses ofPublic Health Concern
an avian influenza A virus infection, they should notify state/local health departments,
collect respiratory specimens from the patient to test at the state health department,
and isolate the patient and follow infection control recommendations. Patients with asuspected infection should begin antiviral treatment as soon as possible.
How can human cases be prevented?

APHIS: Defend the Flock Program
The best way for humans to prevent becoming infected with avian influenza A virus is to
CDC: Information for Specific Groups
avoid contact with sick or dead animals or environments contaminated by them,
CDC: Highly Pathogenic Avian Influenza
particularly in locations where avian influenza outbreaks have been detected. Guidance A(H5N1) Virus in Animals: Interim
is available on protective measures to be taken by individuals with occupational orRecommendations for Prevention,
recreational exposures to animals, including those responding to avian influenza
Monitoring, and Public Healthoutbreaks. Health care workers treating patients suspected or known to be infected with Investigations
an avian influenza A virus should adhere to current infection prevention and control
FDA: Updates on Highly Pathogenic Avianguidance.
Influenza (HPAI)
Are there vaccines available for avian influenza?
Vaccines are available to protect birds from avian influenza, but their use is
discouraged or prohibited in many countries due to practical challenges (e.g.,
vaccinating each individual bird, international trade restrictions, potential exposure
risks to vaccinators) and scientific concerns (e.g., inability to conduct surveillance of
infected versus vaccinated birds, fears of mutation, vaccine effectiveness in multiple
bird species). Countries where avian influenza is endemic have had some success
vaccinating commercial poultry stocks.

Additionally, for human protection, candidate vaccine viruses have been createdthat may be used by pharmaceutical manufacturers to produce pre-pandemic
vaccines that are an essential component of pandemic preparedness. The U.S.
government has stockpiled pre-pandemic vaccines for some avian influenza A viruses
that could be distributed quickly should the virus develop the ability to easily infecthumans and be transmitted easily from person-to-person.

ASPR: Pandemic Vaccines and Adjuvants
Program Overview
CDC: Making a Candidate Vaccine Virus(CVV) for a HPAI (Bird Flu) Virus
FAO: Rational Use of Vaccination forPrevention and Control of H5 Highly
Pathogenic Avian Influenza
WHO: Zoonotic Influenza Candidate
Vaccine Viruses and Potency Testing
Reagents