The number of reported cases of hepatitis B virus (HBV) increased by 9.4 percent across New York City last year, according to new data, suggesting that the liver virus may be a bigger problem in the country’s largest city than previously thought, reports.

Health officials say 8,439 people were newly diagnosed with hepatitis B throughout the five boroughs in 2016 compared with 7,719 new cases in 2015. However, the city’s health department cautioned that these numbers don’t necessarily show that the rate of infection has gone up. Instead, health officials say new HBV screening guidelines and expanded testing targeting immigrant communities where the virus is most prevalent are likely the reason for the increase in diagnoses.

According to the report, Sunset Park in Brooklyn, home to a large Asian community, reported the highest rate of new hepatitis B cases, with 755.7 cases per 100,000 people. Flushing and Greenwich Village also reported a relatively high number of cases compared with the rest of the city.

Meanwhile, new reports of hepatitis C virus (HCV) are declining in New York City, with about 400 fewer cases reported last year than in 2015. As in previous years, the city’s Chelsea and Clinton Hill neighborhoods in Manhattan showed the highest reported rates of hep C.

City health officials say they will continue to urge all New Yorkers, especially those born in countries with high rates of hep B (such as Vietnam, Cambodia, Thailand, as well as many nations in sub-Saharan Africa), to get tested. In addition, the city will continue to test baby boomers, people who use drugs and others at high risk for hepatitis C to help get both hepatitis epidemics under control.