“It may not be absolutely true that those without symptoms can’t transmit the disease, because we don’t have the numbers to back that up,” said Beutler, “It could be people develop significant viremia [where viruses enter the bloodstream and gain access to the rest of the body], and become able to transmit the disease before they have a fever, even. People may have said that without symptoms you can’t transmit Ebola. I’m not sure about that being 100 percent true. There’s a lot of variation with viruses.”

In fact, in a study published online in late September by the New England Journal of Medicine and backed by the World Health Organization, 3,343 confirmed and 667 probable cases of Ebola were analyzed, and nearly 13 percent of the time, those infected with Ebola exhibited no fever at all.