Researchers have been investigating the genetics of the bird flu that has been infecting U.S. cattle, with insights into the spread of the virus. The outbreak in cattle likely began in late December 2023, with cases of low milk production reported in the Texas panhandle. The source of the virus is believed to have been European in origin, emerging in Europe in October 2020 and arriving in the Americas in 2021. The virus has spread to dairy cows in multiple U.S. states, raising concerns about its widespread impact.
The virus has been transmitted from cow to cow and from cows to other animals, including cats, raccoons, poultry, and wild birds. It has caused fatalities in infected cats and raised concerns about the potential for additional species to become infected. The genetic makeup of the virus suggests that it underwent a reassortment event, resulting in a new genotype that has been successful at spreading among cattle. The risk of human infection is considered low, but cases have been reported, including a dairy farm worker who contracted the virus.
Influenza viruses are known for their ability to reassort genetic material, leading to the emergence of new strains with different properties. The H5N1 bird flu virus in cattle represents a unique clade that undergoes reassortment frequently, potentially creating opportunities for the virus to evolve and adapt to new hosts. The virus has been detected in grocery store milk, indicating its widespread presence in the environment.
The spread of the H5N1 virus from birds to cows and its subsequent transmission to other species raises concerns about the potential for further evolution and adaptation. The virus has demonstrated the ability to infect a variety of animals, with multiple instances of spillback events from cattle to other animals. While the risk to humans is currently considered low, ongoing monitoring and research are necessary to understand the full extent of the outbreak and the potential for future changes in the virus.
Efforts to contain the spread of the virus in cattle include new regulations for the movement of dairy cattle and enhanced monitoring of dairy products. The possibility of the virus adapting to spread more easily in mammals, including humans, underscores the importance of continued vigilance and research. Lessons learned from past pandemics, such as COVID-19, highlight the need to remain cautious and proactive in addressing emerging infectious diseases.
