State health officials are urging people to get their annual flu vaccination.
The flu causes over 25,000 deaths a year in the U.S. and has already been seen in New Hampshire this season, according to the state Department of Health and Human Services.
Public Health Director Dr. Jose Montero said that since the virus changes every year and the immunity provided by the vaccines wanes, annual vaccinations are important.
"The vaccine make up is actually reviewed yearly to make sure it matches the strains in circulation and is adjusted accordingly," Montero said. "It is also important that children receiving the flu vaccine for the first time receive two doses because the first dose primes the immune system and the second dose provides the immune protection."
There is also a nasal version available, Montero said.
Dec. 2-8 is National Influenza Vaccination Week. The Centers for Disease Control recommends that anyone age 6 months or older receive an annual vaccine.
Among those most at risk are pregnant women, young children and people who are morbidly obese.