Cases of the flu were close to epidemic levels at the end of 2017, according to the Centers for Disease Control and Prevention.
Specifically, cases of H3N2, a strain of influenza A, are high. H3N2 is especially dangerous and can be harder to contain.
A CDC official told "Good Morning America" this flu season reached its peak about a month earlier than normal. He said recent weather conditions and holiday travel could be to blame.