The state Department of Health confirmed two cases of measles this month on the Big Island, as the disease spreads rapidly on the mainland.

The DOH investigated earlier this month two imported cases of measles in unvaccinated visitors, who were exposed in other states to an “infected international guest,” according to a medical advisory sent to health care providers Jan. 16 by State Epidemiologist Sarah Park.

“Although the visitors were advised to remain isolated and likelihood of exposure to others is low, providers should be aware the period of infectivity while in Hawaii ranged from Jan. 4–13,” she wrote. “Providers are therefore advised to be alert for persons with rash illness and consider and report potential measles infection especially in unimmunized persons.”

Measles, spread airborne by infectious droplets, is spreading across the country, with health officials in Washington state proclaiming a state of emergency Monday. The highly-contagious virus can remain infectious in the air up to two hours after an infected person leaves, the Health Department said.

People with measles are contagious four days before and four days after the onset of rash, which can develop seven to 21 days after exposure.