Avian influenza (bird flu) is a highly contagious viral infection that primarily affects birds. An emerging new lineage 2.3.4.4b of avian influenza has been spreading across the globe since late 2020, carried by migratory birds following specific routes. This panzootic has a significant effect on the avian population with disastrous consequences to the ecology and significant economic loss affecting poultry across the world. In rare instances, the virus can infect mammals from birds causing spillovers, and in recent years, several such instances of spillovers spanning over 200 species have been noted, the most recent being polar bears in Antarctica. Close contact with infected animals could mean the virus could spill over infecting humans and this comes with a significantly large fatality rate.
In late March 2024, a multistate outbreak of H5N1 in dairy cows was detected in the U.S. In what started as a mystery disease affecting dairy herds in Texas, the U.S. Department of Agriculture (USDA) detected the highly pathogenic strain of the virus in herds across the states of Texas and Kansas. The affected animals displayed symptoms including loss of appetite, low-grade fever, and reduced lactation. This marked the first time H5N1 had been detected in cattle, raising concerns about potential transmission routes and the broader impact on the dairy and meat industry. To date, H5N1 has been detected in over 12 herds from six states — Texas, Kansas, Michigan, New Mexico, Idaho and Ohio.
In Texas, other animals in proximity to the affected farms — wild birds and cats — also showed signs of illness and have tested positive for the virus. The exact extent of the spread of H5N1 in cows has not yet been ascertained since cattle are not routinely tested for avian influenza and the symptoms have been relatively mild, leaving possibilities that there may be other undetected infected herds. The initial detections in late March in Texas, Kansas, and Michigan have yet to show a definitive pattern of transmission. Given the pace of the spread of infection across herds, the transmission of the virus within cattle has not yet been ruled out. Investigations are ongoing to determine the exact source of the spread to cows.
