A woman in Maricopa County tested positive for measles last month after visiting Disneyland. That woman has since recovered, but health officials say some of those exposed are still in the incubation period.

The woman, who is in her mid-50s, sought medical care after developing a high fever. Fortunately, she was masked after arriving at the facility, minimizing the virus’ exposure, which can linger in the air for up to two hours.

Still, health officials are actively monitoring the people who came in contact with the woman for at least another week or two. meaning we’re not in the clear just yet.

"In fact, just the opposite, what we do when we identify a case is we identify every single person who could have been in contact with that infected individual, and then we monitor them for 21 days after their exposure," said Dr. Rebecca Sunenshine with the Maricopa County Department of Public Health.

Sunenshine said one reason for the measles outbreak is that parents both here and in Europe are choosing not to vaccinate their kids. One population most at risk for measles: infants too young to be vaccinated.

The Centers for Disease Control says measles was virtually eliminated in 2000 thanks to the MMR vaccine and the ability of providers to detect the virus. But in the 15 years since, things have changed.

"That’s what’s so challenging for physicians is a lot of health care providers have never seen a case of measles and a lot of patients aren’t aware of what measles looks like, so they don’t even think about measles when they getting evaluated," Sunenshine said.

Sunenshine says the cases of mumps and rubella – the other diseases covered by the MMR – are also on the rise, but they are not as contagious as measles.