Measles has once again reached the shores of Hawaii — a reminder that the state is not shielded from the highly contagious disease.

Hawaii is, after all, a travel destination site for visitors from all sides of the Pacific. As measles cases on the U.S. continent continue to grow and circulate, so, too, do the risks of exposure to the measles virus here in the isles.

“We are a major international travel hub and a major destination from the U.S. mainland too,” said state Epidemiologist Dr. Sarah Kemble. “So it is important to remember that measles is just a plane ride away. It may come knocking at our door at any point in time.”

That reminder came earlier this month, on March 7, when the Hawaii Department of Health announced a visitor to Oahu had been diagnosed with measles.

This visitor — a vaccinated adult — had recently arrived in Hawaii “from a region of the continental U.S. with known measles transmission,” according to DOH, and then became ill and sought medical care.

The adult recovered at a private residence on Oahu, and is no longer infectious, according to DOH.

Meanwhile, DOH has sent out a list of places where others might have been exposed in earlier weeks — including both the Honolulu and Hilo airports, the Laie Mormon Temple, a Thai restaurant in Hilo, and Hawai‘i Volcanoes National Park.

With measles, the first symptoms typically show up seven to 14 days after exposure, according to Kemble, but can take as long as 21 days.

The initial symptoms include high fever, cough, runny nose, and red, watery eyes, followed three to five days later by the telltale rash of red spots that spread from the face down to the rest of the body, including arms, legs, and feet.

While breakthrough cases in a vaccinated person are rare, they can happen, Kemble said, for a number of reasons, including the responsiveness of one’s immune system or whether the individual already had a viral infection when receiving the shot.

Breakthrough cases also tend to be mild, as was the case this time. This individual did not have severe illness, she said. DOH, out of an abundance of caution, is still investigating the case and taking all steps to contain it.

“We don’t want to take any chances, and we treat all measles cases as measles cases,” she said.

While no new cases, to date, have been reported as a result of the existing case, DOH will not be able to announce an all-clear until well into April, she said, after two incubation periods have passed.

“We do very actively monitor and communicate with our health care providers in the community throughout these times,” she said. “I think it’s just good to be vigilant. If you’re taking care of patients out there, make sure you’re thinking about measles in case somebody might show up and turn out to have measles.”

Measles in the US

The number of measles cases on the U.S. continent, meanwhile, continue to skyrocket.

As of March 12, the U.S. Centers for Disease Control and Prevention reported 1,362 confirmed measles cases in the U.S. this year. Measles has been reported in 31 jurisdictions — from Alaska to California, Oregon, Washington state, Texas, South Carolina, Florida, New York, and Maine.

South Carolina has had the worst measles outbreak – since its inception in October, the number of cases there ballooned to 993 cases as of March 10, according to the state’s Department of Public Health. The majority of the cases there and in other states are among unvaccinated children under the age of 18.

Last year, Hawaii was one of 45 U.S. states that reported measles cases. There were nearly 50 outbreaks reported in 2025, according to CDC, resulting in three measles­-related deaths.

In April 2025, DOH confirmed measles in a child under age 5 on Oahu upon return from international travel. Eventually, an adult family member of the household also contracted measles, but there were no further cases after that.

“I think we were very fortunate,” said Kemble. “We had followed up on close to 100 contacts from that situation …We had people under monitoring who would have been susceptible, but fortunately, nobody came down with measles.”

Last year, the measles virus also was detected in wastewater samples in West Hawaii County in August, then in samples from Kauai in October, and in samples from West Maui County in November as well as December.

Wastewater monitoring serves as an early-warning system for virus detections, as infected people shed viral genomic material in their waste, regardless of whether they report an illness or exhibit symptoms or not.

No confirmed human cases, however, followed those wastewater detections.

Prior to the latest cases, measles was last detected in the state in April 2023, in an unvaccinated Oahu resident returning from international travel. An exposed resident came down with measles a few weeks later.

Measles is a highly contagious disease, according to CDC, with nine out of 10 people likely to become infected if they are exposed to an infected person and do not have immunity.

It spreads through direct contact with an infected person or through the air via coughs or sneezes. An infected person can spread measles to others from four days before developing the rash to four days afterward.

The virus also can remain in the air for up to two hours after an infected person has left the room.

“Measles always is kind of the big one that we worry about because it’s so contagious,” Kemble said. “And actually, so is chicken pox, but measles is so contagious and more severe. So, you know, one out of 5 people who get measles and are unvaccinated, get hospitalized.”

Possible complications from measles include pneumonia and encephalitis, or brain swelling.

Vaccines waning

Health officials nationwide and in affected states such as South Carolina continue to say vaccines are the best way to prevent measles.

Two doses of the measles vaccine – usually given at the age of 12 to 15 months, followed by another at 4 to 6 years old — is supposed to be 97% effective in preventing disease.

Hawaii’s child immunization rates against measles, however, have been on the decline over the last decade.

Based on the latest CDC data available, Hawaii’s kindergartener vaccination rate for measles, mumps, and rubella for the 2024-25 school year hovers just below 90%, at 89.9%, below the national average. That puts Hawaii on the map with the dozen or so states that have the lowest MMR vaccination rates in the U.S., along with Alaska and Florida.

In South Carolina, where the outbreak began last October, the kindergartener vaccination rate is slightly higher than Hawaii’s, at 91.2%. The target level is 95% or more, according to CDC, in order to reach herd immunity.

Hawaii used to have a consistent vaccination rate of 95% for measles, according to Kemble, but that slipped, and it has been closer to about 90% over the last few years.

“That’s a bit low for the kind of immunity that we want to see to protect the entire community,” she said.

The decline began before the COVID-19 pandemic, and before major vaccine schedule changes made under U.S. Health Secretary Robert F. Kennedy Jr., a longtime vaccine skeptic who continues to pursue a long-discredited theory that vaccines cause autism.

The U.S. is also poised to lose its elimination status for measles, which it has held since 2000, due to the transmission of measles for more than 12 straight months.

Hawaii, as part of the West Coast Health Alliance, still recommends all of the vaccines under the prior Advisory Community on Immunization Practices schedule, in alignment with the American Academy of Pediatrics.

Kemble said the alarming rise in U.S. measles cases is one more reason to check immunization records to see if one is up to date on those two doses, especially for those traveling out of state.

In some cases, a child may be able to get that second dose before age 4, particularly if traveling to an area with measles circulating. For those who may not be able to find their immunization records, getting an extra booster in consultation with their physician does not hurt, she said.

Those planning to travel should check with their doctors on whether an additional or earlier dose of MMR is recommended.

Measles possible exposure sights

What you should know: The first symptoms typically show up 7-14 days after exposure, but can take as long as 21 days. The following is a list of possible measles exposure sites in late February, early March.

Oahu

• Daniel K. Inouye International Airport, “A” gates and baggage claim area, on Feb. 26, from 12:30 p.m.-4 p.m.; Terminal 1 check-in, security, and “A” gates on March 3, from 9 a.m.-12:30 p.m.; and “A” gates and baggage claim area on March 4, from 8:30 p.m.-11 p.m.

• Laie Mormon Temple, on Feb. 27, from 4:30 p.m.- 9 p.m.

Hawaii Island

• Hilo International Airport, gate areas, baggage claim, on March 3, 11:30 a.m.-2:30 p.m.; and at the check-in, security, and gate areas on March 4, 6:30 p.m.-9:30 p.m.

• Hawaii Volcanoes National Park, Visitor Center, Welcome Center at Kilauea Military Camp, and other locations, on March 3, 12 p.m.-6 p.m.

• Hilo Siam Thai restaurant, on March 3, 5 p.m.–9 p.m.

If you were at any of the locations on dates and times specified, watch for symptoms until three weeks after potential exposure. Contact your doctor if you notice symptoms of measles.

The MMR vaccine may prevent or lessen the severity of measles if given within 72 hours of exposure. Immune globulin also may prevent or lessen the severity of measles if given within 6 days of exposure.

Questions? Contact the Hawaii Department of Health Disease Reporting Line at 808-586-4586.

Source: Hawaii Department of Health, Hawai‘i Volcanos National Park