Health officials are urging 7,000 patients of an Oklahoma Dentist to seek medical tests to ensure they haven’t been exposed to hepatitis or the virus that causes AIDS.

The Oklahoma and Tulsa health departments said Thursday that the patients may have been exposed to viruses at clinics operated by Dr. W. Scott Harrington. The agencies said they found “major violations” of the Oklahoma Dental Act.

Spokeswoman Kaitlin Snider of the Tulsa Health Department says Harrington voluntarily closed his practice and is cooperating with investigators.

Letters are being sent to 7,000 patients from Harrington’s clinics in Tulsa and suburban Owasso since 2007. The letters recommend testing for hepatitis B, hepatitis C and HIV. The agencies say it is rare for infections to spread in occupational settings but that tests are important.