Places where lots of animals come into contact can help pathogens move from species to species. So scientists are recreating live-animal markets under laboratory conditions to see how pathogens like coronavirus spread.
Nobody yet knows for sure the definitive origins of the newly recognized coronavirus now known as 2019-nCoV that’s currently spreading across the globe as a human respiratory pathogen. Early reports indicate that the source of the virus was the Huanan seafood market in Wuhan, China, where an eclectic mix of animals including rodents, rabbits, bats and other wild animals and seafood are all on display for consumption and in contact with human shoppers.
Over the past two decades, the world has seen the emergence of multiple pandemic threats, including bird flu (H5N1 avian influenza), SARS, Ebola, Middle East Respiratory Syndrome, chikungunya, Zika and now the new coronavirus from Wuhan. The viruses that cause these diseases, and indeed roughly two-thirds of all recent emergent viruses, originate in animals before they jump to humans.
Each of these events underscores that multiple parts of an ecosystem are at play during an outbreak. For instance, wild bats and rodents harbor numerous viruses that have the potential to infect humans and animals. When these wild animals are extracted from their natural habitat and come into close contact with people, very rare transmission events become much more likely.
These pathogen jumps are complex. They can occur via direct contact, consumption of bushmeat or transmission by insect vectors that carry the germs among a variety of species. And a range of environmental conditions – such as temperature, humidity, sunlight and even seasonal rain and soil conditions – can affect transmission.
Despite the complexity of the natural world, the research approach to understanding how potentially pandemic pathogens and their animal and human hosts interact has been relatively simple. Scientists typically focus on a single species at a time, studied under conditions of constant temperature, humidity and airflow. This strategy has clearly helped researchers understand infectious disease processes.
But as biologists, we believe that more explicitly acknowledging the complexity of the natural world will provide a more robust understanding of emerging infectious diseases. We’ve set up what we call “artificial ecosystems” in the lab to mimic the complicated conditions out in the real world. They’re helping us gather new insights into how viruses and other pathogens actually emerge to become global threats.
Reconstructing live-animal markets and barnyards
It’s undoubtedly rare for pathogens to jump directly from animals in nature into people. But within markets like the one in Wuhan, there are abundant opportunities for the type of interactions that promote pathogen transmission among species.
To mimic these scenarios, we’ve established artificial ecosystems in our lab. That way, we can study the transmission and spread of pathogens, such as influenza viruses, among diverse groups of birds and mammals all housed together and interacting freely.
Because the pathogens we’re studying are potentially deadly and contagious, we need to be very careful they can’t escape from the lab. We establish our ecosystems under strict biocontainment conditions: All exhaust air is filtered and personnel use respirators, wear facility apparel and shower before exiting.