Fifteen more people have tested positive for hepatitis B since the state health department launched an investigation into a North Charleston medical clinic last month, a spokesman for the Department of Health and Environmental Control confirmed.

It brings the total number of positive hepatitis B tests to 18 since May. All the people involved received at least one injection from Tri-County Spinal Care Center on Dorchester Road in North Charleston, the health department said.

DHEC spokesman Jim Beasley said nine of the 18 positive tests have been identified as acute hepatitis B, a more serious form of the disease. The other nine cases are clearing naturally or already have cleared on their own, he said.

Hepatitis B is a “very serious, communicable disease” that affects the liver and can eventually cause cancer, according to the health department.

“It is not possible to determine exactly when these individuals with resolving or resolved infections became infected with hepatitis B; therefore, these cases may or may not be associated with the spinal care center,” Beasley wrote in an email.

Last month, the health department launched an investigation into the Tri-County Spinal Care Center after three patients tested positive for hepatitis B. All three had received similar spinal injections at Tri-County Spinal Care Center on the same dates in February.

The South Carolina State Board of Medical Examiners also stepped in. The board suspended the license of Dr. Richard Stanley Kellett, an anesthesiologist, listed as a staff member on Tri-County Spinal Care Center’s website.

Kellett’s license was previously suspended in 2007 for abusing pain medicine without a prescription.

His recent suspension was ordered on May 21, one day after DHEC issued the public health order, which prohibits Tri-County Spinal Care Center from performing injections of any kind during the investigation.

DHEC has urged all patients who received injections at the clinic since September 2011 to be tested for hepatitis B, hepatitis C and HIV because “several lapses in infection control procedures” were identified at the facility.

In May, a spokeswoman for the clinic estimated that about 500 patients had received injections there since September 2011.

Meanwhile, Tri-County Spinal Care Center continues to accept patients for other services. A second location in Summerville has not been affected by the public health order. Chiropractor Cameron Wills, who owns the clinic, has not returned multiple phone messages.

Reach Lauren Sausser at 937-5598.