A teen is vaccinated at a Cambridge Health Alliance center in Somerville in February. (Photo: Cambridge Health Alliance via Twitter)

Covid-19 cases are beginning to climb again in Cambridge, with 484 new infections in the seven days starting April 2. The increase is probably due to the extremely contagious BA.2 omicron subvariant, which now dominates cases in the region, a spokesperson for the Cambridge Public Health Department said Friday.

“The [Centers for Disease Control and Prevention] estimates that BA.2 now accounts for over 84 percent of the cases in the Northeast, so we do believe that the increase in cases is related to this variant,” spokesperson Dawn Baxter said. “BA.2 is highly transmissible but is a mildly symptomatic variant, especially for individuals who are up to date on vaccinations and boosters.”

Scientists believe that BA.2 is 30 percent to 50 percent more transmissible than original omicron, which itself was much more contagious than any other variant or the ancestral virus.

Baxter said the increase hasn’t created “strain on the health care system.” The number of Covid-19 patients hospitalized at Cambridge Health Alliance declined from Tuesday to Thursday, from 10 patients to six, according to the state health department. At Mount Auburn Hospital the Covid-19 census has barely changed, alternating between five and six.

The most recent federal figures on hospital capacity, for the last week of March, show that the hospitals are filled with other patients as well as people being treated for Covid-19: Cambridge Health Alliance had an average 45 beds available out of 233, or about 19 percent, and seven of 13 intensive-care unit beds were filled, leaving six. Occupancy was tighter at Mount Auburn Hospital, with only 24 of 197 inpatient beds free, or 12 percent, and seven of 21 ICU beds available, or one-third.

Baxter said the health department isn’t considering recommending a return to the city’s indoor mask mandate “at this time,” but does “continue to recommend that residents assess their personal and household risk and wear masks in certain circumstances if they or household members are vulnerable to serious illness from Covid-19.”

Besides that advice, “we strongly encourage our residents to get a booster dose whenever they become eligible,” Baxter said. The health department is offering free vaccinations by appointment for the “Cambridge community” from 2 to 4 p.m. Wednesdays at 119 Windsor St. Cambridge Health Alliance will vaccinate Massachusetts residents at 176 Somerville Ave., Somerville, or at its pharmacies at Cambridge Hospital and the East Cambridge clinic. The pharmacies are for those 18 and over and accept walk-ins. The Somerville site serves anyone 5 and older; appointments are recommended.

CHA also offers vaccinations in Malden and at other locations outside Cambridge and Somerville. Full details of CHA’s vaccination program are here.