HELENA — Montana is now reporting 15 cases of measles, including two hospitalizations, according to the Montana Department of Public Health and Human Services. The location of the hospitalizations has not been reported.

The rising number of cases comes as the CDC urges people who are unvaccinated against the disease to avoid air travel.

The warning follows at least four cases at two airports, including Denver, where people have either transmitted or contracted the virus.

This year marks the first time in almost 35 years that any cases of measles have been reported.

On Monday, Hill County reported two new cases; both were unvaccinated children.

Nationwide, there are now nearly 1,100 known cases in 33 states. More than half of those cases are in people ages 19 years and under.

According to Johns Hopkins Medicine, measles is one of the most contagious of all known infections. Health officials also say it is a very preventable infection, thanks to vaccination.

According to Johns Hopkins Medicine, measles is one of the most contagious of all known infections. Health officials also say it is a very preventable infection, thanks to vaccination.

Measles can lead to serious health complications like pneumonia and encephalitis, which is swelling of brain tissue that can leave lasting damage and be fatal in some cases.