• The H3N2 variant has been associated with more severe flu seasons for children and the elderly in the past, according to the CDC.
• Public health labs have detected H3N2 in 76% of the more than 3,500 respiratory samples that have tested positive for the flu and were analyzed for the virus subtype
• The flu hospitalization rate has surged to a decade high this season.

A variant of the flu that hits kids and seniors worse than other strains of the virus is dominant in the U.S. right now, setting the country up for a potentially bad flu season.

Public health labs have detected influenza A(H3N2) in 76% of the more than 3,500 respiratory samples that have tested positive for the flu and were analyzed for the virus subtype, according to a surveillance report published Friday by the Centers for Disease Control and Prevention.

The H3N2 variant has been associated with more severe flu seasons for children and the elderly in the past, according to Dr. Jose Romero, director the CDC's National Center for Immunization and Respiratory Disease.

"There are also early signs of influenza causing severe illness in precisely these two groups of individuals this season," Romero told reporters on a call earlier this month.

The flu hospitalization rate has surged to a decade high this season. Overall, about 8 people per 100,000 are being hospitalized with the flu right now but seniors and the youngest children are much harder hit than other age groups, according to CDC data.

The hospitalization rate for seniors is more than double the general population at 18 per 100,000. For kids younger than age five, the hospitalization rate is about 13 per 100,000.

At least 4.4 million people have fallen ill with the flu, 38,000 have been hospitalized, and 2,100 have died since the season started. Seven kids have died from the flu so far this season.

"When we have more H3N2, we usually have a more severe flu season — so longer duration, more children affected, more children with severe disease," said Dr. Andi Shane, a pediatrician and infectious disease expert at Children's Healthcare Atlanta.

The other influenza A variant, H1N1, is generally associated with less severe seasons compared with H3N2, Shane said. H1N1 makes up about 22% of sample that have tested positive for flu and were analyzed for a subtype, according to CDC.

The percentage of patients reporting symptoms similar to the flu, a fever of 100 degrees or greater plus a sore throat or cough, is the highest in Virginia, Tennessee, South Carolina, Alabama and Washington D.C right now, according to CDC.

Respiratory illnesses are also very high in Arkansas, Colorado, Georgia, Kentucky, New Jersey, Maryland, Mississippi, New Mexico, North Carolina and Texas, according to CDC.

The CDC recommends that everyone 6 months or older get a flu shot. Children younger than age 8 who are receiving the vaccine for the first time should get two doses for the best protection.

The flu vaccine is normally 40% to 60% effective at preventing illness, but people who do still get sick are less likely to end up in the hospital or die, according to the CDC.

Public health officials are also encouraging people to stay home when they are sick, cover coughs and sneezes and wash hands frequently. Those who want to take extra precautions can consider wearing a facemask indoors in public.