In this March 2, 2021, file photo, a pharmacy technician loads a syringe with Pfizer's COVID-19 vaccine at a mass vaccination site at the Portland Expo in Portland. Credit: Robert F. Bukaty / AP

AUGUSTA, Maine — Four cases of the delta COVID-19 variant have been detected in Maine, the state’s top health official said Wednesday, raising concerns that the more contagious strain of the virus could spread here among unvaccinated people.

Nirav Shah, director of the Maine Center for Disease Control and Prevention, said the four cases recorded in Maine so far are likely an undercount but show that the “concerning” variant has established itself in the state and may soon become a main source of cases.

The new strain of the virus, which was first detected in India earlier this year, may account for a fifth of U.S. cases, federal officials said earlier this week. Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, characterized the strain as the “greatest threat” to U.S. efforts to eliminate the threat of COVID-19. Early studies from other countries have suggested it is both more transmissible and more likely to cause hospitalizations.

The three vaccines used in the U.S. protect against the delta variant, health officials say, but it may be more likely to spread among unvaccinated people. Just shy of 60 percent of Mainers are fully vaccinated, according to the latest federal data, while more than 450,000 here have not received any doses of the vaccine.

Shah said people who have not yet been vaccinated should take the opportunity to get the vaccine as soon as possible in order to avoid risk from the variant.

“It’s only a matter of time before it takes greater hold here in Maine and causes an increasing number of cases among those who are not vaccinated,” he said.

Shah said the state would be unlikely to reimplement travel restrictions to try to prevent the spread of the virus at this point because there were no “hot spots” from which blocking travel was likely to help and the virus is already spreading here.