A Long Island hospital has asked more than 4,200 patients to get tested for HIV and the hepatitis B and C viruses (HBV and HCV) after admitting they were potentially exposed to contaminated blood by a nurse at the facility, RT.com reports.

A spokesman for the South Nassau Communities Hospital in Oceanside, New York, said patients receiving treatment for their diabetes between March 2011 and January 2014 might have had a re-used insulin pen used on them. This mistake could have exchanged body fluids between multiple people.

The hospital has now banned the use of insulin pens in favor of single-use insulin vials to avoid the mistake. It also has set up a toll-free hotline for potentially exposed patients to schedule free blood tests. According to hospital officials, no one so far has tested positive for any of the viruses.

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