Hawaii health officials are urging residents to stay vigilant and get vaccinated as measles cases are on the rise across the United States.

The state Department of Health is warning that the state remains at risk for a travel-related measles case, which could lead to an outbreak due to the virus’s extreme contagiousness and suboptimal vaccination coverage.

The highly contagious viral illness, which was declared eliminated in the U.S. in 2000, has been making a troubling comeback as vaccination rates decline.

Measles cases in the U.S. have surged in recent years. In 2023, the Centers for Disease Control and Prevention reported 59 cases nationwide, but that number spiked to 285 in 2024. As of March 13, there have already been 301 confirmed cases across 15 states.

Internationally, the World Health Organization reported 10.3 million measles cases worldwide in 2023. The highly infectious nature of the virus means even a single case brought into Hawaii could rapidly spread within the community.

An infected individual can transmit measles up to four days before and after symptoms appear, and the virus can linger in the air for up to two hours after an infected person leaves an enclosed space. The CDC estimates that if one person has measles, nine out of ten nearby individuals who are not immune will become infected.

State health officials remind residents that if they suspect they have measles, they should call ahead before visiting a clinic to prevent further spread.

“As a doctor and governor, I want to be clear: measles is a serious, highly contagious disease, and cases are rising worldwide. It spreads fast, causes severe complications, and puts our keiki, kupuna, pregnant women, and those with weakened immune systems at risk,” Gov. Josh Green said in a statement. “Prevention is the best cure, and a measles outbreak is preventable. The best protection is vaccination. Two doses of the MMR vaccine are 97% effective in preventing infection and stopping the spread. Measles was once eliminated in the U.S., but low vaccination rates are bringing it back. We can’t let that happen here in Hawaiʻi.”

For communities to be protected from a measles outbreak, at least 95% of the population must be vaccinated. Hawaii’s measles, mumps and rubella — or MMR — vaccination rate for kindergartners was 90% during the 2023-2024 school year, below the national average of 93%.

Some areas, including schools on Maui, Kauai, and Hawaii island, have even lower vaccination rates, some below 75%, making these communities especially vulnerable.

The DOH is urging all Hawaii residents, particularly parents, to ensure their children are fully immunized.

“High vaccination rates not only protect vaccinated individuals but also safeguard the broader community,” the department said in a release.