Officials say thousands of patients at South Nassau Communities Hospital are at risk for a deadly infection.

The hospital located in Oceanside sent a letter to more than 4,000 patients urging them to get a blood test. According to the hospital, the patients may have been exposed to HIV, as well as hepatitis B and hepatitis C.

Those who may be affected could have received insulin from a shared insulin pen.

The hospital says there's no evidence of anyone actually reusing an insulin pen, but a nurse was reportedly overheard saying it was OK to do so. Insulin pens used on people with diabetes are prefilled, and are meant to be used on a single patient. Because of the potential backflow of blood into the pen after the injection, using it on multiple people may expose them to bloodborne infections.

The hospital says the risk of infection is low, but they are urging patients to get a free blood test.