Thousands of people got a particularly crummy gift this Christmas: A warning that they could have been exposed to dangerous bloodborne diseases like HIV and viral hepatitis while receiving care at the hospital.

On Tuesday, NBC News reported that the HealthPlus Surgery Center in Saddle Brook, New Jersey sent letters to more than 3,700 patients who had visited it between January 1st to September 7th. According to the letter, obtained by NBC News, an investigation by the New Jersey Department found that HealthPlus staff often failed to properly sterilize surgical tools between uses or otherwise neglected infection control procedures, raising the risk that patients could have gotten bloodborne infections.