State health officials are advising nearly all Connecticut residents to again wear masks indoors as the COVID levels continue to rise. Fairfield, Windham and Tolland counties were added Friday to the Centers for Disease Control and Prevention's list of areas with "substantial" COVID spread. The list now includes all Connecticut counties except Middlesex and Litchfield. In the counties where there is substantial spread, there have been more than 50 cases per 100,000 people over a seven-day period. The state Department of Public Health advised Friday that anyone over the age of 2 who lives, works or travels through the affected counties should wear a mask in indoor public settings. State residents with underlying medical conditions that put them at risk from the virus, or people who live with people at high risk, should wear masks indoors, the agency said. "This includes vaccinated family members who live with young children who are not yet eligible for vaccination," the statement said. Connecticut's upward trend of COVID cases and hospitalizations continued Friday. The state numbers showed a daily positivity rate of 2.72 percent as 491 new infections were diagnosed out of 18,025 tests. Four more patients increased the state's hospitalization total to 116. Gov. Ned Lamont has so far resisted issuing a renewed statewide mask mandate. A Lamont spokesperson said Friday the governor's stance has not changed and referred to the DPH guidance recommending people wear masks indoors in the affected counties. Only unvaccinated people are required to wear a mask indoors statewide. Masks are required in some public settings, such as state courthouses, municipal buildings, health care facilities, public transit and transportation hubs. But some venues and cities have started to reinstate universal masking as a result of the new CDC guidance. Norwalk Mayor Harry Rilling said Friday he was reinstating a mask mandate at all city properties for everyone - "vaccinated or unvaccinated" - beginning Monday. "The delta variant and other variants of concern have changed the trajectory of the pandemic and our understanding of this virus," Rilling said in a statement. "While it remains likely that those who are fully vaccinated will be protected from severe illness from COVID-19, they may still have the potential to transmit it to others." In Hartford, residents received a voice message from Mayor Luke Bronin urging them to mask up indoors. "If you go to a restaurant, grocery shopping or the store- follow the CDC's guidance and wear your mask," Bronin said. He also urged people to get vaccinated, calling it "the only way to beat this pandemic." The Connecticut Science Center in Hartford said in a Facebook post Friday that it has reinstated a universal mask policy "until further notice." Anyone over the age of 2, including staff and visitors, must wear a mask regardless of whether they've been vaccinated, the post said. In a statement Friday, CDC Director Dr. Rochelle P. Walensky said the agency's new guidance released this week was partly based on data from a recent outbreak in Cape Cod, the majority of which involved fully vaccinated people. Some 469 infections were linked to large public events in a Massachusetts town in Barnstable County, the report said. Of those, 74 percent involved fully vaccinated people. The report said testing showed the delta variant was found in 90 percent of 133 infected people. Cases of delta comprise more than 73 percent of Connecticut cases sequenced in the past three weeks, according to the latest data from the Yale School of Public Health. The alpha strain, previously dominant in Connecticut and elsewhere in the country, comprised only around 10 percent of cases sequenced during the same time period. In the majority of Connecticut's 169 municipalities, vaccination rates are above 60 percent, according to the latest state data released Thursday. But in Mansfield, Sterling, Thompson, Hartford, New Britain and Plainfield, less than half of residents have started vaccination, according to the state's data. Along with the rest of New England, Connecticut still has among the most vaccinated populations in the nation. Nearly 70 percent of all Connecticut residents had started vaccination as of Thursday, according to the CDC. About 63 percent are now considered fully vaccinated, the data shows. Weekly vaccine administrations have slowly risen over the past two weeks, but still hover below 40,000 doses per week - far below the peak of more than 315,000 weekly doses in early April. In some communities, nearly everyone is vaccinated. In Salisbury, Lyme, Old Saybrook and Kent, more than 80 percent of residents have started vaccination, the data shows.