The number of measles cases in the U.S. has reached a 33-year record high, years after it was officially eliminated in the country, prompting public health experts to sound the alarm that other diseases could experience a similar resurgence.

While measles symptoms typically resolve in a few weeks, the virus can cause pneumonia, making it difficult for patients, especially children, to get oxygen into their lungs. It may also lead to brain swelling, which can cause lasting damage, including blindness, deafness and intellectual disabilities.

Health experts say the true case count may be higher. Measles was considered eliminated in the U.S. in 2000, but if cases continue to rise at the rate it has, that status could change. The United States just reported its highest number of measles cases in more than three decades.