Korea Centers for Disease Control and Prevention (KCDC) announced Friday its interim epidemiologic survey on the former Seoul Hyeondae Clinic, which was under suspicion of having a hepatitis C outbreaks due to reused syringes.

The survey started when the National Health Insurance Service reported the clinic on suspicion that the hospital was reusing syringes to the Ministry of Health and Welfare last year. Later, the ministry requested an epidemiologic survey to the KCDC after finding a relatively large number of hepatitis C patients who were treated at the clinic from 2011 to 2012, while analyzing the insurance agency’s big data.

The investigation is ongoing as the clinic, which closed in 2014, reopened under the name JS Clinic. Although the owners of the two hospitals are different, there have been allegations that the two have a connection as the former owner of the Seoul Hyeondae Clinic works at the new clinic from time to time.

The interim report showed that out of the 7,303 patients examined, 335 tested positive for hepatitis C antibody. The survey expects to examine 14,455 patients who visited the clinic from 2011 to 2012. The positive rate of hepatitis C antibody for the hospital was 4.6 percent, which was 7.7 times higher compared to the 0.6 percent hepatitis C antibody-positive patients of the general population in Korea.

Of the 335 patients, 125 tested positive for hepatitis C virus, while the rest tested negative. Having the hepatitis C virus means that the patient has the disease.

KCDC’s investigation into the medical records from the clinic confirmed that the clinic performed several procedures that led to the transmission of hepatitis C.

Hepatitis C outbreak due to reused syringes has been prevalent in Korea. In 2015, 99 patients treated at Dana Hyeondae Clinic in Seoul tested positive for hepatitis C antibody. A year later, more than 400 patients treated at Hanyang Orthopedics Clinic in Wonju, Gangwon Province, tested positive for hepatitis C antibody.