We’ve all noticed the increase in egg prices over the past year, but who or what is to blame? Many scientists point to a species of influenza for birds. Avian influenza A, also known as “avian flu” or “bird flu,” is an influenza virus commonly separated into highly pathogenic avian influenza (HPAI) and low pathogenic avian influenza (LPAI), depending on the virus’ severity in birds. As with any influenza virus, it is classified into sub-types based on the type of surface proteins known as hemagglutinin (H) and neuraminidase (N), in this case H5N1. Most strains of H5N1 avian influenza are considered low pathogenic; however, a more severe strain of HPAI H5N1 was first discovered in Southern China in 1996 causing outbreaks in China and Hong Kong, and in 2003 H5N1 re-emerged causing several outbreaks in Asia. While several other sub-types have been circulating in bird populations, recently H5N1 has again become the predominant virus in avian populations around the globe.
Avian Influenza’s Impacts
Avian influenza can be a dangerous and fatal disease for birds. Per the CDC, since January 2022 (the most recent outbreak of bird flu), there have been 57,868,714 confirmed H5N1 infections in birds in the United States. Rarely, humans have contracted the virus from infected birds, most commonly on chicken farms. Like seasonal influenza, symptoms of avian influenza vary from person to person; however, in general symptoms tend to be more severe compared to seasonal flu, ranging from mild fatigue and muscle aches to severe pneumonia and death. Globally, 863 human cases of avian influenza have been documented since 2003. The first human case in the United States was documented in April 2022 in an individual working with infected chickens.
Causes for Concern?
Highly pathogenic H5N1 has been identified in many species of wild bird, including ducks and geese, and even other wild animals, such as racoons, bears, and even seals on the Russian coast. Thus far, human infections appear limited to human-bird interactions (e.g., those working on poultry farms). No human-to-human transmission of H5N1 has been documented, and it is unlikely that an outbreak of human infections would occur. However, this virus is becoming more prevalent and dangerous in birds. Globally, there were more cases of bird flu in 2020-2021 than the four previous years combined. In the United States, this disease is putting strain on poultry farms; since February 2022, it’s estimated that roughly 43 million hens have either died from the disease or been culled to prevent additional spread. Consequently, egg production was down by 29% in December 2022 compared to January 2022. Thus, even as HPAI H5N1 currently poses no risk of becoming a human health crisis, it is emerging as a bird health crisis, and is even impacting our grocery shopping.
Taylor is a medical student at the University of Texas Medical Branch in Galveston. She is hoping to pursue her interest in infectious diseases by specializing in Internal Medicine or Pathology.
Sources
Centers for Disease Control and Prevention, National Center of Immunization and Respiratory Disease (14 June, 2022). Information on Bird Flu. Centers for Disease Control and Prevention.
Economic Research Service, US Department of Agriculture (11 January, 2023). Avian influenza outbreaks reduced egg production, driving prices to record highs in 2022. The United States.
Food and Agriculture Organization of the United Nations (26 January 2023). Global Avian Influenza Viruses with Zoonotic Potential situation update. United Nations.
Schnirring, L. (9 January 2023). USDA reports more H5N1 avian flu in mammals, including bears. Center for Infectious Disease Research & Policy, University of Minnesota.
Schnirring, L. (24 January 2023). Avian flu strikes more poultry in 6 states as virus found in dead seals in Russia. Center for Infectious Disease Research & Policy, University of Minnesota.
United States Department of Agriculture (April 2015). USDA Avian Influenza Fact Sheet. The United States of America.
World Health Organization, Eastern Mediterranean Regional Office (2023). Avian Influenza. The United States of America.
World Health Organization (27 April 2022). Disease Outbreak News; Avian Influenza A (H5N1). The United States of America.