What Is Spillover? Bird Flu Outbreak Underscores Need for Early Detection to Prevent the Next Big Pandemic

Most spillover research today is focused on learning about and preventing viruses – including coronaviruses, like the one that causes COVID-19 and certain viral lineages of avian influenza – from jumping into humans. These viruses mutate very quickly, and random changes in their genetic code could eventually allow them to infect humans.

Spillover events can be hard to detect, flying under the radar without leading to bigger outbreaks. Sometimes a virus that transfers from animals to humans poses no risk to people if the virus is not well adapted to human biology. But the more often this jump occurs, the higher the chances a dangerous pathogen will adapt and take off.

Spillover Is Becoming More Likely
Epidemiologists are projecting that the risk of spillover from wildlife into humans will increase in coming years, in large part because of the destruction of nature and encroachment of humans into previously wild places.

Because of habitat loss, climate change and changes in land use, humanity is collectively jostling the table that is holding up that cup of water. With less stability, spillover becomes more likely as animals are stressed, crowded and on the move.

As development expands into new habitats, wild animals come into closer contact with people – and, importantly, the food supply. The mixing of wildlife and farm animals greatly amplifies the risk that a disease will jump species and spread like wildfire among farm animals. Poultry across the U.S. are experiencing this now, thanks to a new form of avian flu that experts think spread to chicken farms mostly through migrating ducks.

Current Risk from Bird Flu
The new avian influenza virus is a distant descendant of the original H5N1 strain that has caused human epidemics of bird flu in the past. Health officials are detecting cases of this new flu virus jumping from birds to other mammals – like foxes, skunks and bears.

On Feb. 23, 2023, news outlets began reporting a few confirmed infections of people in Cambodia, including one infection leading to the death of an 11-year-old girl. While this new strain of bird flu can infect people in rare situations, it isn’t very good at doing so, because it is not able to bind to cells in human respiratory tracts very effectively. For now, the Centers for Disease Control and Prevention thinks there is low risk to the general public.

Active monitoring of wild animals, farm animals and humans will allow health officials to detect the first sign of spillover and help prevent a small viral splash from turning into a large outbreak. Moving forward, researchers and policymakers can take steps to prevent spillover events by preserving nature, keeping wildlife wild and separate from livestock and improving early detection of novel infections in people and animals.

Treana Mayer is Postdoctoral Fellow in Microbiology, Colorado State University. This article is published courtesy of The Conversation.