Nearly 500 of the state's 3,318 confirmed cases of the flu are in Mid-Missouri.
The federal Weekly Influenza Report shows Central Missouri has had 494 cases, with roughly 2.9 percent of all emergency room visits reporting flu-like symptoms.
At Capital Region Medical Center, more than 130 patients have reported flu-like illnesses in the last three days and 37 percent of them have tested positive for the flu, said Valerie Lyon, infection preventionist for the hospital.
"The flu season is here at Capital Region," Lyon said. "It is probably a little bit more this year. ... Influenza A has mutated so that particular strain is not covered real well in the vaccination, so with that we have respiratory hygiene stations in all of our waiting rooms, and our staff has protocols that they follow to help prevent transmission of that within our facility.
"We know it is going be a rough flu season."
Although the vaccine is not as effective as usual, it is still recommended by health officials. Vaccinated people who have contracted the mutated virus have had less severe symptoms, according Jessi Kempker, immunization coordinator for the Cole County Health Department. Other advice for the season is to stay home if you are sick, wash your hands frequently, and try not touch your face, Lyon said.
Influenza A has mutated from the normal H3N2 virus, causing this year's flu vaccine's effectiveness to decrease, according to a health advisory from the Centers for Disease Control (CDC).
The CDC reported influenza activity is currently low in the country as a whole, but increasing in some areas. They also reported that Influenza A (H3N2) is most frequently reported and has been found in every state.
From Oct. 1 through Nov. 22, around 48 percent of the CDC analyzed samples of the flu were of the influenza A vaccine component, but the rest were antigenically drifted, meaning different from what the vaccine covered.
"There are just like small changes in the virus, and the body cannot catch those differences, but still getting the vaccine is more beneficial," Kempker said. "We are seeing more cases of influenza A compared to previous years. Typically it is more common to see more influenza in January and February verses December and November."