A recent study published in Science and funded by the National Institutes of Health (NIH) has found that a single alteration in a protein on the surface of the highly pathogenic avian influenza (HPAI) H5N1 virus—currently present in U.S. dairy cows—could significantly increase its potential for human-to-human transmission.
These findings highlight the critical importance of ongoing surveillance and monitoring of HPAI H5N1 for genetic changes that might enhance its ability to spread among humans.
At present, the bovine (cow) H5N1 virus is not capable of human-to-human transmission. However, infections have been documented in individuals exposed to infected wild birds, poultry, dairy cows, and other mammals. As part of global pandemic preparedness efforts, researchers have long studied H5N1 to track natural genetic mutations and assess their potential impact on transmissibility.
Influenza viruses attach to cells with a surface viral protein called hemagglutinin (HA). The HA latches on to sugar (glycan) molecule receptors on cells to cause infection. Avian (bird) influenza viruses—like H5N1—have not infected people often because the human upper respiratory tract lacks the avian-type cell receptors found in birds. Scientists are concerned that viruses could evolve to recognize human-type cell receptors in the upper airways and acquire the ability to infect people and spread between them.