Avian influenza, sometimes referred to as “bird flu,” is a disease caused by influenza A viruses. It can be highly contagious and has a history of infecting birds, wildlife, and humans. A subtype of avian influenza, H5N1, was first detected in 1996 in Guangdong Province in China and has been spread globally by migratory birds. A 2021 outbreak of H5N1 that originated in Europe has caused a panzootic in birds that spread to the United States in early 2022. H5N1 is widespread in wild birds and is responsible for outbreaks in poultry and dairy cattle in the United States. Since 2022, according to the U.S. Department of Agriculture (USDA), H5N1 has infected over 19,000 wild birds across the United States, 2,236 commercial and backyard poultry flocks (affecting more than 208 million birds), and 813 mammals (e.g., domestic cats, harbor seals, mountain lions). Since March 2024, USDA has also confirmed the virus in 1,168 cattle herds across 20 states. Human infections have been comparatively rare: 71 reported cases and two deaths since 2024, according to the Centers for Disease Control and Prevention, occurring mostly among dairy and poultry workers exposed to infected animals. H5N1 is not known to spread easily from human to human, but its ability to adapt, mutate, reassort with other viruses, and infect different mammal species means that the potential for human-to-human transmission exists. Some Members of Congress have expressed concerns about the spread of H5N1 and its potential health effects on humans, as well as its possible negative economic impact on agriculture, especially in the poultry and livestock industries. Some Members also expressed concern about avian influenza when previous pandemics occurred. Avian influenza is part of the Orthomyxoviridae family and is grouped into four main categories: A, B, C, and D. Type A viruses are known to infect birds and mammals (including humans), while Types B, C, and D are restricted to certain host ranges. Type A viruses include avian influenza, swine influenza, and canine influenza. Type A viruses have caused more documented global pandemics in human history than any other type of pathogen, including four pandemics since the beginning of the 20th century. Highly pathogenic avian influenza (HPAI) can cause high mortality rates in wild birds and poultry, while low pathogenic avian influenza (LPAI) typically causes few or no clinical signs. Avian influenza is globally spread by birds that fly long distances via migratory pathways. These pathways can also be conduits for the spread of avian influenza to mammals (including humans) from wild birds. H5N1 is responsible for a recent outbreak circling the globe. Federal, state, and local agencies are responding to H5N1 in various ways, including monitoring the spread of H5N1; creating policies to address potential impacts in industries such as poultry; and contemplating countermeasures for addressing the disease in animals and potentially humans. Several bills introduced in the 119th Congress address aspects of avian influenza and other types of outbreaks, including those pertaining to poultry farmers and farms affected by avian influenza (S. 574/H.R. 1376 and S. 1904), federally funded research (H.R. 2868), disease surveillance and mitigation efforts (H.R. 766), and coordination among agencies (S. 4451). There are several issues that Congress might consider when addressing avian influenza in the United States: the effectiveness and coverage of existing biosurveillance practices and policies; the effectiveness of coordination among federal agencies; the status of international collaboration; U.S. withdrawal from the World Health Organization; research and data required to fill existing knowledge gaps; activities related to monitoring and planning for potential spillover of avian influenza to humans; and policies that lead to suppressing or eliminating avian influenza in the United States. Some of these policies include heightening surveillance and detection of infected organisms; increasing biosecurity measures to protect livestock and poultry from infected wild birds and mammals; limiting exposure of wildlife associated with humans (e.g., livestock, poultry, and pets) to H5N1; instituting rapid response and containment protocols of infected animals, including efforts to cull infected animals; creating and testing mitigation and treatment methods, such as vaccines and therapeutic remedies; and conducting research on mutations and genetic reassortment to provide insight into whether human-to-human transmission of the virus is imminent.
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