Raina Plowright

Professor of Veterinary Medicine

Raina Plowright, professor in the Department of Public and Ecosystem Health at Cornell University, studies how to prevent zoonotic spillover – the critical first step in the emergence of pandemics.

Plowright says:

“This is why scientists worry not only about new viruses, but also about old viruses in new contexts. A cruise ship creates conditions of prolonged close contact in crowded indoor environments. That does not mean widespread transmission will necessarily occur, but it changes the epidemiological context in ways that deserve careful attention. 

“Hantavirus is an example of a pathogen that spills over frequently from animals to humans but historically has not spread efficiently between people. This incident reminds us that context matters. The same virus in a different context can behave very differently.

“We have seen this repeatedly with emerging infectious diseases. Ebola outbreaks remained relatively limited for decades until the virus entered densely connected urban populations. SARS-CoV-1 spread internationally only after a superspreading event in a Hong Kong hotel. Mpox expanded locally after population immunity declined (as the proportion of the population having the smallpox vaccine declined) and globally after viral evolution increased human-to-human transmission.

“The broader concern is that there are likely tens of thousands of animal viruses with some potential to infect humans. Most may currently exist in contexts where spillover is unlikely or invisible, and the right circumstances have not arisen for sustained transmission. But rapid environmental change, global travel, urbanization, ecological disruption, and changing human behavior are constantly creating new interfaces between people, animals, and pathogens. This is the central concern behind ‘Pathogen X’ – the possibility that an existing virus encounters the right ecological or social conditions to emerge suddenly as a major threat.”