A Long Island hospital sent out warning letters to 4,247 patients alerting them to the possibility that they may have been exposed to HIV, hepatitis and other dangerous illnesses. According to CBS, South Nassau Communities Hospital in Oceanside is asking for those patients to get blood tests after it was discovered that an insulin pen might have been reused on multiple patients.

Officials are concerned that patients might have received insulin shots from an insulin pen reservoir that might have been reused rather than a single-use needle, between March 2011 and this January.

Among the many Long Islanders who received the letter was Cynthis Shub, who said she was shocked to see the concerns listed in the letter.

"I see 'shared' and 'patients' - the neighbors could have heard me scream," she said.

Shub received an insulin shot at the hospital last year.

"I see hepatitis, I see HIV, I'm like, 'Are you kidding?'" she added.

Another patient, who did not want his identity revealed, said it was "very shocking, and very disturbing" to receive the letter from the hospital.

"Someone screwed up somewehere," he said, CBS reports.

Hospital officials said concerns were sparked after a nurse was heard saying that insulin pens ca be used on several different patients. Typically, insulin is kept in a chamber for multiple uses on the same patients.

"It just doesn't make sense that something like this could happen like this nowadays. It's not like something that's not known; don't share this stuff," a woman told WCBS 880 Long Island Bureau Chief Mike Xirinachs, CBS reports. "And the hospital did it. You know, if people do it, it's one thing. A hospital does it? It's a little ridiculous."

Due to similar incidents happening at other hospitals, the Food and Drug Administration and the Center for Disease Control both had to issue reminders to hospitals between 2009 and 2012. In the letter, the agencies said it had been become "increasingly aware of reports of improper use if insulin pens" that "must never be used on more than one person," according to CBS.

"When you use the pen for more than one patient, you have the possibility of introducing the bodily fluids from someone else into another individual," Dr. Alison Myers with the North Shore LIJ Health System said.

A spokesperson from South Nassau said no one actually witnessed the pen being reused and that fresh needles had been used for each patient. The letters were just a precaution.

"The risk of infection from this is extremely low," the hospital said in a statement. "Nonetheless, out of an abundance of caution, the hospital is recommending that patients receiving the notification be tested."

Following the incident, the hospital is not using the pen anymore and is now using single-use insulin syringes. They are asking for patients to schedule a test within 60 days of receiving the letter and to call the toll-free number, 516-208-0029, to schedule the blood test.