Humans infecting animals infecting humans: Preventing pandemics requires protecting all species
When the World Health Organization declared COVID-19 a pandemic on March 11, 2020, humans had been the only species with reported cases of the disease. Less than two weeks later, a report from Belgium marked the first infection in a domestic cat – presumably by its owner.
Researchers have documented this phenomenon of human-to-animal transmission, colloquially referred to as spillback or reverse zoonotic transmission, in both domestic and wild animals. This stepping-stone effect provides new opportunities for pathogens to evolve and can radically change how they spread.