After being declared eliminated in the United States in 2000, one of the most highly contagious viruses, measles, is making a comeback.

Measles cases continue to rise in the United States and internationally, according to the Hawaii Department of Health.

In 2023, four outbreaks and 59 cases of measles were reported in the U.S. In 2024, there were 16 outbreaks and 285 cases.

As of March 13, 2025, the Centers for Disease Control and Prevention has reported 301 confirmed cases across 15 states. The World Health Organization reports cases are increasing globally with 10.3 million cases worldwide in 2023.

DOH officials say the risk of a travel-related measles case coming to Hawaii is increasing and the risk of an outbreak is high because of how contagious the virus is and Hawaii’s low vaccination rate against it. Someone infected with measles can spread the virus up to four days before and four days after experiencing symptoms.

If a person becomes infected with measles, nine out of 10 people nearby who do not have immunity will also become infected, says DOH. The measles virus can also stay airborne and infectious for up to two hours after an infected person leaves an enclosed area.

In order to prevent an outbreak, the more infectious a virus is, the higher the percent of the population needs to be vaccinated. For measles, the vaccination rate of a population needs to be at least 95% to protect the wider community from an outbreak.

DOH says the state’s measles, mumps and rubella vaccination rate for kindergarteners was 90% for the 2023 to 2024 school year, which is below the national average of 93%.

In some pockets of the state, vaccination rates are even lower. DOH says multiple schools on Maui, Kauai and Hawaii Island report vaccination rates below 75%, which is lower than the 82% vaccination rate in Gaines County, the epicenter for the Texas-New Mexico outbreak. Any outbreak on a neighbor island would severely strain its healthcare system and no neighbor island hospital has a pediatric intensive care unit.

“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, kūpuna, pregnant women, and those with weakened immune systems at risk,” said Governor Josh Green, M.D., in a release.

“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 Hawaii,” Green said.

Because of the rising measles cases in the U.S., DOH issued a medical advisory to healthcare providers on March 11 to identify and report any measles cases and ensure all patients — especially those planning international travel — are up to date with the MMR vaccination.

Symptoms of measles usually begin seven to 14 days after exposure. The first sign is usually a high fever accompanied by a cough, runny nose and red, watery eyes. A red rash usually appears a few days later, starting on the face and upper neck, then spreading to the arms and legs.

In the U.S. about one in five unvaccinated people who contract measles is hospitalized due to complications such as pneumonia. Other complications include ear infections that can lead to loss of hearing and, rarely, encephalitis (brain swelling), even death. Newborns too young to get vaccinated are at increased risk. A measles infection during pregnancy is associated with increased risk of miscarriage, stillbirth and low birth weight.

There have been no reported cases of measles in Hawaii as of March 17. DOH advises people to call their healthcare provider ahead of time if they suspect they have measles. This will start the process to determine whether they indeed have measles and also allow the clinic to prepare for an in-person visit and prevent spread.

DOH urges all residents to get up to date on immunizations, especially children.

Visit the DOH website for more information on measles and vaccinations.