New health data shows flu activity in the United States has started to rise again, including a noticeable increase in the Hudson Valley.

Health officials say hundreds of people have recently been diagnosed with the flu across Westchester, Orange, Rockland and Dutchess counties.

Westchester County has reported the highest number of cases, with dozens of patients requiring hospitalization.

Orange County is also seeing a significant number of diagnoses, followed by Rockland and Dutchess counties, where hospitalizations have also been reported.

The Centers for Disease Control and Prevention says influenza B strains are slowly increasing nationwide.

Experts warn that even people who have already had the flu this season could get sick again if they are exposed to a different strain.

Health officials say the current flu vaccine provides protection against two A strains and one B strain of the virus.