An undisclosed amount of Broward General Medical Center patients tested positive for infectious diseases following treatment by Qui Lan, a nurse who reused IV bags and tubing while administering chemical stress tests, The Miami Herald reports. Broward General is located in Fort Lauderdale.

Officials estimate that 1,851 patients getting stress tests from 2004 through early September of this year might have been exposed to HIV, hepatitis B or hepatitis C. The hospital has recommended screening for all of these patients and has thus far received results for 250 of them.

Hospital spokesperson Cathy Meyer would not reveal the number of positive results for these blood-borne infections. She said that it was unclear whether these positive results are linked directly to Lan or if patients contracted the blood-borne illnesses through other means.