Beginning in the fall of 2002 there was a pandemic of severe acute respiratory syndrome coronavirus (SARS-CoV), which causes a very severe version of pneumonia. Starting in southern China, the disease spread to 33 countries, affecting 8094 and killing 774. The virus belongs to the coronavirus family which is the same as the common cold. SARS symptoms include respiratory distress, fever, diarrhea, and malaise. Now researchers say that bats are the origin of the pandemic.

Bats have long been suspected as a natural reservoir for coronaviruses. They have already been connected in hosting Nipah and Hendra, Ebola, and now researchers have discovered a closely related virus in Chinese horseshoe bats which can infect human cells that causes a SARS-like illness known as Middle East Respiratory syndrome (MERS). MERS has killed 62 people since its emergence in 2012.

In 2005, a virus was discovered in horseshoe bats which is 88-92% genetically identical to SARS-CoV. Included in the 8-12% difference is the genetic code for the “spike” protein which allows the virus to infect human cells. In fact, these regions were incredibly dissimilar. This led scientists to believe that bats may have been indirectly responsible and palm civets may have acted as an intermediate for the virus to mutate into something that could cause illness in humans.

A recent study published in Nature details an experiment in which researchers gathered fecal samples from Chinese horseshoe bats in search of coronaviruses. In the region that codes for the spike protein, these samples were much closer to the SARS-CoV. The team was able to isolate a live virus and use it to infect kidney cells in pigs and bats, but they were also able to infect human lung cells.

While this study is not able to determine if an intermediate was used a decade ago with the SARS pandemic, the new paper shows that civets may not have been necessary for the virus to spread from bats to humans.

Some scientists are skeptical and say that what can happen in the lab is not necessarily likely to happen in nature. Many bats carry rabies, which can readily infect human tissue, but transmission is exceedingly rare. However, the more science understands about the characteristics of coronaviruses may allow scientists to better predict and potentially prevent another SARS-like pandemic.