Indian scientists are raising concerns about the increasing threat of bird flu spreading to humans, highlighting recent findings on the evolving H5N1 virus. Researchers at the Indian Institute of Science (IISc) in Bengaluru have identified specific genetic mutations in the currently circulating 2.3.4.4b clade of the H5N1 avian influenza virus that could significantly increase its potential to infect humans.
The IISc team, led by Kesavardhana Sannula, analyzed nearly 43,000 protein sequences, including those from birds, non-human mammals, and human influenza strains. Their analysis focused on identifying rapidly changing amino acids, which indicate regions under "selection pressure," and tracking how these mutations are distributed across the viral proteins. The scientists then categorized the mutations as either adaptive, meaning they help the virus infect humans, or as barriers, meaning they hinder cross-species spread.
Their research indicated that the 2.3.4.4b clade is acquiring key mutations similar to those found in pandemic human influenza strains, suggesting a growing risk. Ranjana Nataraj, the study's first author, emphasized that this particular branch of the virus is increasingly adapting to non-human mammals, raising concerns about potential human adaptation. The study also revealed that certain animal hosts, particularly foxes, may harbor H5N1 strains with a higher potential for adapting to humans. This is especially concerning as Indian foxes are commonly found in agricultural areas near human settlements, potentially increasing the risk of exposure for rural populations.
The H5N1 virus spreads from infected birds and non-human mammals to humans, with human-to-human transmission being rare. The World Health Organization (WHO) has reported 972 confirmed human cases of H5N1 influenza, with 468 deaths, between 2003 and February 2025. India has reported two deaths in 2021 and 2025, caused by the 2.3.2.1b H5N1 variant. The researchers are advocating for proactive and targeted surveillance, particularly in mammals, that could serve as "stepping stone" hosts for the virus's adaptation to humans. They also caution that a bird flu outbreak could be more challenging to manage than the COVID-19 pandemic.
Another recent study has indicated that bird flu may be spreading silently from animals to humans, with some individuals, such as veterinarians, showing no symptoms. This highlights the possibility of undetected infections and the need for increased vigilance. Experts recommend precautions for those in contact with sick or dead birds, including wearing respiratory and eye protection and gloves when handling poultry. While the current risk to the general public remains low, health officials urge continued caution and monitoring of the virus's evolution.
