In October 2022, Dr. Marcela Uhart witnessed a heart-wrenching scene on the beaches of Argentina’s Valdés Peninsula: thousands of dead and dying elephant seals, victims of the H5N1 bird flu virus. This outbreak marked a grim milestone in a global epidemic that has killed millions of birds and now threatens marine mammals and potentially humans.
H5N1 has rapidly infiltrated a wide range of hosts, from wild birds to dairy cows, and has proven capable of infecting mammals. In South America, it has killed hundreds of thousands of seabirds and tens of thousands of sea lions. The scale of these outbreaks suggests that the virus has adapted to spread among marine mammals.
Genetic studies indicate that the virus in marine mammals has acquired mutations not seen in birds, suggesting transmission between mammals. Sick elephant seals and sea lions have been found shedding high levels of virus, and scavengers may play a role in its spread.
The virus continues to evolve and may acquire mutations that allow it to jump to humans. While the current risk of human transmission is low, experts emphasize the need for vigilance. Preexisting immunity to seasonal flu strains may provide some protection, but the virus could still cause severe disease in vulnerable populations.
The H5N1 outbreak in dairy cows highlights the potential for interspecies transmission. Pigs, susceptible to both human and avian flu strains, could provide a mixing ground for viral gene exchange. Lack of timely and transparent reporting of animal outbreaks hampers efforts to monitor and mitigate the spread.
To prevent a human pandemic, experts call for increased monitoring, international cooperation, and proactive measures. They urge leaders to act swiftly when faced with emerging threats and to balance caution with due diligence. By respecting the virus’s capabilities and taking appropriate precautions, we can manage its spread and protect public health.
