The city says Hepatitis B is a bigger problem in the five boroughs than it previously thought.
Health officials say more than 8,400 people tested positive for the infection last year, up more than 9 percent from 2015.
Sunset Park, Brooklyn saw the highest increase.
Flushing and Greenwich Village also reported a high number of cases.
They say the rise is likely because of new screening guidelines and expanded testing targeting immigrants from countries where the disease is more common.
But Hepatitis C is on the decline, with about 400 fewer cases reported last year than in 2015.
Hepatitis B and C are most commonly spread through infected blood.
Doctors recommend not sharing personal items like razors, and avoid reusing needles and medical supplies.
Hepatitis can also be prevented by practicing safe sex and not drinking large amounts of alcohol.