Some businesses, including Raven Used Books in Harvard Square, continue to ask for customers to wear masks despite the end of a broad indoor mask mandate. (Photo: Marc Levy)

Cambridge has ended its indoor mask mandate, but the Cambridge Public Health Department is all but telling residents to keep it alive. In an announcement Friday, the department applauded the fact that many residents continue to mask up, saying: “The Cambridge Public Health Department strongly supports this practice!”

The announcement went on to recommend that people “wear a mask when indoors outside your own home, including on public transportation.” That was the rule before the city eliminated the indoor masking requirement on March 13 (it ended on March 28 in city buildings) and before a judge struck down the federal mask mandate on public transportation Monday and the MBTA followed suit.

The department urged residents to use high-quality masks such as KN95 and KF94 that can filter out 90 percent to 95 percent of viral particles. Cloth masks are okay for outside use where distancing is possible, but they don’t protect against transmission of the omicron variant indoors, it said. Omicron has accounted for almost all cases since January; a more contagious subvariant called BA.2 now dominates in New England.

As the department said, new Covid-19 cases among city residents have been rising and “taking measures to support yourself is a smart choice.” The announcement didn’t mention it, but deaths have also been rising: Two more residents have died since April 14, including one person who was living in a long-term care facility. The total for Cambridge now stands at 163 deaths.

The department said Cambridge “is a highly vaccinated city and we are not seeing pressure on the health care system at this time.” Still, it urged residents to get tested if they have symptoms or have been exposed to the virus; isolate or quarantine if they test positive; and get vaccinated and boosted.

The precautions are especially important for people over 65 and those with underlying health conditions or compromised immune systems and for people who aren’t vaccinated because they face higher risk from the virus, the department said.

The percentage of fully vaccinated and boosted residents has been rising slowly for weeks; certain age groups and ethnic communities continue to lag. The most recent vaccination report April 21 showed that only 53 percent of older teens from 16 to 19 are fully vaccinated, compared with 77 percent of residents citywide. People in their 20s, who have the highest number of new cases, have full vaccination and booster rates below the overall citywide percentage. Hispanic residents continue to have lower vaccination rates as well.

The department’s announcement also urged higher-risk people who test positive to seek treatment as soon as possible. It recommended they call their doctor or a state number with information on where to find drugs that protect infected people against severe disease. The telephone number is (508) 213-1380.