Connecticut’s flu season is rapidly getting worse, with three deaths attributed to the virus through the middle of December, according to statistics compiled by the state Department of Public Health.

There were 355 laboratory confirmed cases of the flu in Connecticut and a total of 144 people were hospitalized with the virus through Dec. 16, according to the most recent report from the state health department. That compares to 255 confirmed cases and 98 hospitalizations a week earlier.

The Centers for Disease Control recently announced that Connecticut is among 23 states with “widespread” flu activity, which means the virus is prevalent in all corners of the state. The percentage of emergency room visits attributed to the flu has climbed to 5.6 percent statewide.

“It is turning out to be a very active season, no question about it,” said Alan Siniscalchi, an epidemiologist at the state health department.

With the holiday season in full swing, officials said it is still not too late to get a flu shot and urged residents to do so at a time when many people are spending extended periods of time indoors with family.

“If you haven’t gotten it already we strongly encourage everyone to get the flu shot,” Siniscalchi said. “We expect flu season to peak in mid-January or a little bit later. If you get it now you may be timing it just right for the upcoming peak.”

Bitter cold temperatures are expected for the remainder of this week, which can make it easier for the flu virus to be transferred.

“Studies suggest that when the air is cold and the humidity is very low … the flu virus will survive longer, remain airborne longer and then is more likely to be picked up and inhaled by other individuals,” Siniscalchi said.

Dr. Rick Martinello, medical director of epidemiology and infection control at Yale-New Haven Hospital, said he anticipates another uptick in cases next week when children return to school, where the virus can quickly infect a whole classroom, particularly if sick children don’t stay home.

“Stay home when you’re sick,” he said. “If your children are sick, keep them home from school. It’s much easier to say it than to do it,” but it’s important, he said.

The young and the elderly are most susceptible to the flu. The three deaths in Connecticut this season all involved people older than 65.

Preliminary data from the southern hemisphere has shown that this year’s flu vaccine may not be as effective as prior ones, but Siniscalchi and Martinello said that doesn’t mean people should skip it.

“There’s a growing amount of evidence showing that if you are vaccinated” and still get the flu “it decreases the severity of the disease that one experiences,” Martinello said.

Connecticut’s increase in flu activity mirrors what is being seen nationally, where flu season has come early and aggressively.

The CDC reported more than 13,400 confirmed cases of the flu nationwide through Dec. 16, more than six times the number of reported cases at that time last year. And the strain of flu virus that has been most prevalent so far – H3N2 – is typically more severe.