Travel plans? Here's what to know as measles exposures reach trains and games

The safest way to protect yourself from measles when traveling is to be vaccinated. Malte Mueller/Getty Images hide caption

The U.S. is in the midst of the worst measles resurgence in decades. Recent outbreaks in several states and exposures in places like bars, sports stadiums and on public transit have some people questioning the safety of travel or how they should prepare for upcoming plans.

The Centers for Disease Control and Prevention lists over 3,600 confirmed measles cases in the U.S. as of Sept. 24 — and two deaths as of Sept. 28. Almost all of those cases have been among unvaccinated individuals.

The CDC notes the number of deaths is subject to change as more information becomes available and after it completes more reviews. It's important to note that the Pennsylvania Department of Health has counted four measles-associated deaths so far. The CDC has disputed whether measles actually caused those deaths.

In the last two weeks, Pennsylvania, Ohio and New York have had the most cases, according to the Johns Hopkins Bloomberg School of Public Health U.S. measles tracker .

The true number of cases across the country is likely higher, according to Dr. Paul Offit , director of the Vaccine Education Center at the Children's Hospital of Philadelphia and a professor of pediatrics at the Perelman School of Medicine at the University of Pennsylvania.

"I think if anything, we're underestimating how many people are actually being exposed, and how many people are being infected, and how many people are being hospitalized and dying," he said.

He said that's because many children, parents or adults may not seek medical care if they get infected.