News that a nurse in full protective gear had become infected with the Ebola virus raised some disturbing questions on Monday. Has the virus evolved into some kind of super-pathogen? Might it mutate into something even more terrifying in the months to come?

Evolutionary biologists who study viruses generally agree on the answers to those two questions: no, and probably not.

The Ebola viruses buffeting West Africa today are not fundamentally different from those in previous outbreaks, they say. And it is highly unlikely that natural selection will give the viruses the ability to spread more easily, particularly by becoming airborne.

“I’ve been dismayed by some of the nonsense speculation out there,” said Edward Holmes, a biologist at the University of Sydney in Australia. “I understand why people get nervous about this, but as scientists we need to be very careful we don’t scaremonger.”