The coronavirus spreading in China and the SARS outbreak of 2003 have two things in common: Both are from the coronavirus family, and both started in wet markets.
At such markets, outdoor stalls are squeezed together to form narrow lanes, where locals and visitors shop for cuts of meat and ripe produce. A stall selling hundreds of caged chickens may abut a butcher counter, where uncooked meat is chopped as nearby dogs watch hungrily. Vendors hock skinned hares, while seafood stalls display glistening fish and shrimp.
Wet markets put people and live and dead animals — dogs, chickens, pigs, snakes, civets, and more — in constant, close contact. That makes it easy for a virus to jump from animal to human.
On Wednesday, authorities in Wuhan, China — where the current outbreak started — banned the trade of live animals at wet markets. The specific market where the outbreak began, the Huanan Seafood Market, was shuttered on January 1. The coronavirus that emerged there has so far killed 17 people and infected nearly 550.
“When you bring animals together in these unnatural situations, you have the risk of human diseases emerging,” Kevin Olival, a disease ecologist and conservationist at the EcoHealth Alliance, told National Geographic. “If the animals are housed in bad conditions under a lot of stress, it might create a better opportunity for them to shed virus and to be sick.”
Coronaviruses are zoonotic diseases, meaning they first spread to people from animals. In the case of SARS, and likely this Wuhan coronavirus outbreak as well, bats were the original hosts. The bats then infected other animals, which transmitted the virus to humans.
Here’s what Chinese wet markets look like.