When the newborn piglets first started getting sick in October 2016, farmers in China’s Guangdong province suspected porcine epidemic diarrhea virus (PEDV) — a disease they’d seen in the pigs before. And, at first, the tests did come back positive for PEDV. But then something strange happened. By January 2017, the pigs stopped testing positive for that virus — but kept getting sick.

Researchers began looking for another cause of the piglets’ illness. The four farms where the pigs were dying were located about 60 miles from Foshan — the place where severe acute respiratory syndrome (SARS), first emerged back in 2002. Before it was halted in 2004, SARS spread to 33 countries and sickened more than 8,000 people, killing 774. Read more at NPR’s Goats and Soda.