The health and safety of Hawai‘i residents are a top priority as measles cases continue to rise in the United States and internationally as the highly contagious viral illness is returning after being declared eliminated in the United States in 2000.

In 2023, four outbreaks and 59 cases of measles were reported on the mainland. The numbers rose to 16 outbreaks and 285 cases in 2024. As of March 13, 2025, the Centers for Disease Control and Prevention reported there are already 301 confirmed cases across 15 states so far this year. Measles cases are also increasing globally with the World Health Organization reporting 10.3 million cases worldwide in 2023.

The risk of a travel-related measles case in Hawai‘i continues to increase, and the risk of an outbreak in Hawai‘i from exposure to a travel-related measles case has increased due to the very high contagiousness of measles and the low vaccination rate against measles. Individuals infected with measles can spread the virus up to four days before and four days after the presence of symptoms.

Measles is one of the most contagious viruses currently known. If a person is infected with measles, an expected nine out of 10 people nearby who do not have immunity also will become infected. The measles virus can remain airborne and infectious for up to two hours after an infected person leaves an enclosed area.

The more infectious a virus is, the higher the percent of the population that needs to be vaccinated to prevent an outbreak. For measles, a population vaccination rate of at least 95% is needed to protect the community from an outbreak. The state’s measles, mumps, and rubella (MMR) vaccination rate for kindergartners was 90% for the 2023-2024 school year, below the national average of 93%.

Vaccination rates in Hawaiʻi are even lower in some pockets. Notably, multiple schools on Maui, Kauaʻi, and Hawaiʻi Island report vaccination rates below 75%, which could lead to greater vulnerability. This is below the 82% vaccination rate in Gaines County, which is the epicenter for the Texas-New Mexico outbreak.

Measles is an acute viral respiratory illness. Symptoms usually begin 7-14 days after exposure. The first sign is typically a high fever, often accompanied by a cough, red, watery eyes and a runny nose. A red rash usually appears a few days later, starting on the face and upper neck and spreading to the arms and legs.

In the United States, about 1 in 5 unvaccinated people who contract measles are hospitalized due to complications, such as pneumonia. Other complications include ear infections that can lead to hearing loss and rarely encephalitis (brain swelling) and even death. Newborns who are too young to get vaccinated are at increased risk, and a measles infection during pregnancy is associated with an increased risk of miscarriage, stillbirth, and low birth weight.

Due to the rise in measles cases in the United States, including the rapidly expanding outbreak in Texas and New Mexico, the Hawai‘i Department of Health (DOH) issued a medical advisory to healthcare providers on March 11. The advisory emphasizes identifying and reporting cases and ensuring that all patients without other evidence of immunity — especially those planning international travel — are up to date with measles, mumps, and rubella (MMR) vaccination.

Many other illnesses can mimic measles, and currently, no cases of measles acquired in Hawai‘i have been reported. If you suspect you may have measles, it is important to call ahead to your healthcare provider so they can begin the process of determining whether measles is present and advise you on steps to prevent its spread in the clinic before your arrival.

DOH urges all residents, particularly parents, to ensure their children are up to date on immunizations.