When you study something that is, in the strictest sense, invisible, answers to seemingly straightforward questions quickly become elusive.
Like: What makes one virus replicate more efficiently than another? And why do some people get really, really sick—while others are able to fight off the same illness with few symptoms?
“Oh, there are lots of questions,” said Vincent Munster, the chief of the Virus Ecology Unit at the National Institute of Allergy and Infectious Disease, when I asked him to describe the sorts of things that still have virologists puzzled about the MERS virus. MERS refers to Middle East Respiratory Syndrome, a new and potentially deadly virus that has killed at least nine people and sickened dozens more in South Korea since last month, prompting travel warnings and a massive quarantine order. Symptoms can include fever, cough, and shortness of breath—just like many other less serious viruses, which makes MERS difficult to diagnose at first.
“Here's a very important question,” Munster said. “How does this virus spread so easily between healthcare settings?”
MERS has only been observed in humans since 2012, and the recent cases in South Korea represent the largest outbreak of the virus ever outside of Saudi Arabia, where it originated in camels before jumping to humans. “For dromedary camels, [MERS is] very much like what we get in a common cold,” Munster said. “But if it comes into humans, it moves into the lower respiratory tract where it can cause some harm. If you are relatively healthy, you probably don't get too sick from this virus. But if you have co-morbidities—let's say a heart condition, diabetes, or obesity, maybe all three—the outcome for you if you get this virus is increasingly worse.”