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(CNN) – The Centers for Disease Control and Prevention believes the incubation period for MERS is about five days, but it could last as long as two weeks.
"We're not taking any chances, and we're just watching people for a full 14 days," says Dr. David Swerdlow, head of MERS response activities at the CDC.
"We don't know exactly how it's transmitted, and who could get the virus ... we're monitoring everybody, we're asking everybody to take temperatures, to call the health department if they get sick," says Swerdlow.
For those monitored for 14 days, the CDC is also collecting blood samples to see if anybody actually was infected with the virus.
The chance of MERS spreading is generally low unless you're a health care worker with a MERS patient, or someone who would be in close contact with that patient.
But a professor at Harvard raised concerns about MERS may possibly mutate into something much more serious.
"We have been monitoring for any changes in the virus all along. And so far, there's no evidence that there's been any change," says Swerdlow.
"We're always watching for any chance that there could be evidence of ... sustained human-to-human transmission. That would be the marker that something has changed. And we have been very vigilant for that," says Swerdlow.
For more from Dr. David Swerdlow, check out the video above.