The delta variant of the coronavirus, which has quickly become the dominant strain in other countries and may cause more severe illness, is spreading in Hawaii, according to the Hawaii Department of Health.

There have been three cases of the delta variant associated with travel from the continental U.S. and one case confirmed in an Oahu resident with no history of travel, according to a Health Department press release. In the travel-related cases, two were on Oahu and one was on Hawaii island.

The Health Department said it was investigating the cases to determine the extent of household and community transmission.

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While no one required hospitalization, they did have symptoms. Only one of the four people was fully vaccinated.

“A recently published study from Scotland found that the risk of COVID-19 hospital admission was approximately double in those with the Delta variant when compared to those with the B.1.1.7 strain, also known as the U.K. or Alpha variant,” said State Laboratories Division Administrator Edward Desmond in an email.

The delta variant was first detected in India and now makes up 10% of all cases in the U.S. Health officials have warned that it could become the dominant strain in the country.

The current vaccines have proven effective in protecting people from contracting the variant, or in “breakthrough” cases, becoming seriously ill.

“Given what we know about the Delta variant and the cases already identified in Hawai‘i, we expect to detect additional cases in the coming weeks,” said acting State Epidemiologist Sarah Kemble in an email. “Our best defense against of the variants is to get vaccinated as soon as possible.”

State health officials detected the first case of a delta variant in Hawaii earlier this month.

Information on where to get vaccinated can be found at this link.