The Evolution of Highly Pathogenic Avian Influenza in Recent Years in the New Geographical Regions of the World and in New Species
Keywords:
avian influenza, highly pathogenic, panzootic, pandemic.Abstract
Highly pathogenic avian influenza H5N1 dominated the global epidemiological picture between 2004-2006. The carriers of the flu are migratory birds; the virus being located in the intestines of birds. The H5N1 subtype is extremely contagious for birds. It does not normally affect humans, but since 1997 there have been cases of transmission of the virus to humans, most of whom have had direct contact with infected birds or surfaces contaminated with H5N1. The H5N1 virus was first isolated in 1996 on a goose farm in the Guangdong region of China, and since 1997 this type of infection has been reported in humans. Highly pathogenic avian influenza H5N1, also known as "bird flu", has led to the death of hundreds of millions of birds globally in recent years. Its spread to humans and other mammal species, including cattle and pigs in the United States. Between 2023 and early 2025, the world experienced a sustained and unprecedented panzootic evolution of highly pathogenic avian influenza (HPAI) H5N1 (clade 2.3.4.4b). This period was marked by the spread of the virus to new geographic regions—including Antarctica and South America—a significant increase in infections among mammals and sporadic cases in humans, which raised concerns among health officials.
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