The most com flu virus this year is influenza A -- primarily the H1 viruses, Cox said. "The influenza activity we have seen in the United States has been relatively mild in comparison to last season," Catharina Cox, director of the U.S. But, the experts also said they're keeping a close watch on bacterial infections such as methicillin-resistant Staphylococcus aureus (MRSA). "That is unusual for this time of year and is indicative of a relatively mild influenza season," she said. MRSA is resistant to certain antibiotics and can strike flu patients -- particularly hospitalized ones -- and is potentially fatal.

This is one of the groups of viruses included in this year's. The national baseline is about 2.4% -- the percent of patients with flu symptoms seen by doctors, Cox said. So far, the states with the most cases of flu are New Jersey and Virginia, Cox said, adding that hard numbers are difficult to come by, so health officials are relying on anecdotal reports. Centers for Disease Control and Prevention's Influenza Division, said during a teleconference.

Also, deaths from pneumonia associated with influenza are well below the epidemic level, Cox said.

The number of patients with flu that doctors are seeing is also well below the seasonal baseline.