Flu activity in Connecticut has earned a “widespread” designation for seven straight weeks, prompting state health officials to remind residents it’s never too late to get vaccinated.

From Jan. 5-11, the most recent week for which the state Department of Public Health has posted statistics, 171 flu-related hospitalizations and six deaths were reported. Since October, 643 hospitalizations and 13 deaths — including one in New London County — have been associated with the illness.

Flu viruses could continue to circulate as late as May.

“It’s turning out to be a very active season in Connecticut and across most of the country,” Alan Siniscalchi, the department’s influenza surveillance coordinator, said Friday. "It’s unusual to have such quickly rising levels of activity at this point in the season.”

But while it may be unusually prevalent this year, the flu is not as severe as it’s been the last couple of years, Siniscalchi said.

In 2017-18, a particularly devastating flu year, Connecticut recorded 175 flu-related deaths, the most of any year in the decade since the state started tracking the illness. In 2018-19, the state recorded 87 flu-related deaths, the second-most in its history.

The severity of the flu in any given year has to do with the prevalence of various strains, some of which are more deadly than others. Seasons in which the Influenza A (H3N2) virus is common tend to take a toll on the elderly and are associated with more deaths, Siniscalchi said. Such strains as Influenza B and A variant (H1N1) cause lots of cases but fewer deaths.

“This year, we’re seeing a lot of cases among school-age children and college-age (adults),” he said.

Flu outbreaks typically begin in heavily populated areas and spread. State health officials define the level of activity as “widespread” in any week in which new outbreaks of flu and flu-like illnesses are reported in at least half of the state’s eight counties. The most cases have been documented in the most populous counties — Fairfield, Hartford and New Haven — while “New London County has seen a good amount,” Siniscalchi said.

“I’ve gotten more reports of flu than ever before. I’m definitely seeing an uptick,” said Kris Magnussen, communicable disease prevention supervisor for Ledge Light Health District, which serves East Lyme, Groton, Ledyard, Lyme, New London, North Stonington, Old Lyme, Stonington and Waterford.

Magnussen said the district receives reports of flu cases from hospital laboratories and doctor’s offices but has no way of telling whether a flu victim has been vaccinated. The effectiveness of this year's vaccine won't be known for some time yet.

“I’ve been seeing a lot of Influenza B, which you usually see at the end of the season, so that’s unusual,” she said. “We used to say you should have the shot up until the end of March, but people can get flu all year long. We don’t stop giving the shot until we don’t see any more flu.”

Children and the elderly — those with weak or compromised immune systems — are most susceptible to flu. Infants as young as 6 months old should be vaccinated, according to health officials.

Dr. Craig Mittleman, medical director of Lawrence + Memorial Hospital’s Emergency Department, said he’s seen an increase in the number of patients who test positive for flu, though he cautioned that not all patients are tested. At the end of last week, 233 patients had tested positive, nearly three times the number who had tested positive at the same point a year ago.

“Like in most situations, the elderly and the young are the most vulnerable, and that’s the population we target with testing,” Mittleman said. “This (flu) season started earlier, more quickly (than last year).”

Beyond getting an annual flu shot — October's a good time since it takes a couple of weeks for full immunity to develop — the steps for warding off flu are generally well known, if not always well practiced.

“Wash your hands,” Magnussen said. “It’s so simple, and people don’t do it. They blow their nose and then touch everything. Flu can live on surfaces for up to 24 hours, so that’s why cleaning is so important.”

Cover your mouth when coughing and your nose when sneezing and “practice social distancing,” Siniscalchi said. When you're sick, stay home from school or the office.

b.hallenbeck@theday.com