The predominant strain of flu this year is an influenza A (H3N2) virus, which has accounted for 76 percent of the reported viruses.
"We know H3N2 has been associated in previous seasons with pretty severe illness, particularly among the elderly. That could be a contributor to why we are seeing such high levels of activity right now," Jhung said.
Currie of Montefiore suspects the H3N2 strain may also pose more of a risk for younger people, who "don't have as much experience with that strain."
Fortunately, flu experts did a good job last spring of predicting which of the flu strains circulating in Asia would be most likely to cause disease in this flu season. As a result, the CDC says the current batch of flu vaccines appear to be a good match for this year's flu.
So far, 91 percent of flu viruses analyzed by the CDC match flu strains contained in this year's vaccine.
