Health officials said Thursday that they are investigating a “probable” third case of monkeypox found in an adult on Oahu who had no history of travel, raising concern the virus may be spreading locally.

The first two people believed to have the viral disease had close contact with each other, and one had traveled to an area on the mainland with confirmed cases, officials said Thursday at a press conference.

The Centers for Disease Control and Prevention confirmed that the initial case was monkeypox, officials said. Samples from the other two patients also have been sent to the CDC for confirmation, with results expected within five days.

The third case had no history of travel but had attended a social gathering, according to the state Department of Health.

“This person does not have a travel history. The reason that’s significant is that it tells us that monkeypox is probably in our community,” Health Director Libby Char told reporters.

The department was still investigating whether the third person had contact with the other two.

“We are investigating links between this third case and the first two cases,” deputy state epidemiologist Nathan Tan said in a press release. “Individuals at increased risk should avoid anonymous sexual contact or events where individuals may have close bodily contact with others.”

The first patient to show monkeypox symptoms had been admitted to the Triple Army Medical Center, but the other two “probable cases” were not hospitalized, according to epidemiological specialist Joe Elm.

Monkeypox is a rare disease but has spread from Africa, where it’s endemic, and has been reported in 31 other countries. As of Thursday, the CDC confirmed 45 cases of monkeypox in the U.S.

Since monkeypox is closely related to smallpox, vaccines are considered effective at protecting people against the virus.

Char said that the vaccinations are not recommended for the general public but can prevent “or at least limit the severity of infection” if administered after exposure.

“We’re doing contact tracing to identify those that are at high risk and likely would benefit the most from being vaccinated,” she said.