Public health officials are recording a busy flu season and again urge people to seek vaccinations if they haven’t already received one.

“This year we are seeing much more flu compared to last year with two new flu strains,” Dr. Gale Burstein, Erie County health commissioner, said Friday in a written statement. “Fortunately both of these new flu strains are part of this year’s vaccine.

“The key to preventing influenza is vaccination,” she said. “The vaccine is widely available today in physicians’ offices, pharmacies and various community sites.”

New York is among 29 states, up from 16, which reported high levels of influenzalike illnesses for the week of Dec. 23-29, and nine states reported moderate levels, according to the U.S. Centers for Disease Control and Prevention in its latest FluView report. The 29 states with high levels included Vermont, Pennsylvania and New Jersey.

Nationwide, 18 children have died this season with flu-associated illnesses, the CDC said.

For the fourth straight week, the proportion of people seeing a health care provider for influenza-like illness rose above the national baseline, the CDC said. Although most people usually recover from flu without complications, the virus poses more risk for people younger than age 2, those over 50, pregnant women and people with weakened immune systems or chronic medical conditions.

State Health Commissioner Nirav R. Shah is among public health officials who urge anyone over 6 months of age to seek vaccination for the season. (Children under 6 months of age cannot receive the vaccine.) Health officials say vaccinations are especially important for family members and people who regularly come in contact with young children or individuals in those high-risk categories.

The state Health Department said last year was a mild year for the flu in New York. Still, there were 1,167 flu-related hospitalizations, and one child died. Thirty-four children in New York died over the last four years, when the state averaged more than 4,400 flu-related hospitalizations a year.

While last year was mild, health experts braced for a tough 2012-13 because the Southern Hemisphere had a severe bout with flu. “What happens there is often an indication of what’s ahead for us in the Northern Hemisphere,” Burstein said in October, the traditional start of the annual flu season.

Flu season generally runs through May and often spikes in late winter or early spring. Immunity develops about two weeks after vaccination and protects against influenza for the rest of the season. So it is not too late to get immunized for this year, Burstein said.

“Even healthy people,” she said, “can get very sick from the flu and spread it to others.”