We’ve all heard of MRSA, but what about VRSA?

It stands for vancomycin-resistant Staphylococcus aureus, which is a rare staph infection. So far, only a handful of cases have cropped up across the country, with the latest one involving a patient at Pennsylvania Hospital in Philadelphia.

The patient, who is on kidney dialysis, was transferred from Delaware and did not catch the infection at the University of Pennsylvania-owned hospital, The Philadelphia Inquirer reported.

As the name implies, VRSA is resistant to the antibiotic, vancomycin, which is commonly used to keep patients with weak or no kidney function from getting bacterial infections.

“The infection is not particularly virulent and is susceptible to existing antibiotics,” Neil Fishman, an infectious-disease expert at Penn told the newspaper. “VRSA has never been transmitted from one person to another."

Fishman said the resistant form appears to develop in a patient with two infections: the more common MRSA and drug-resistant bacteria known as vancomycin-resistant Enterococcus or VRE.

"Vancomycin-resistance genes from the VRE are transferred to the MRSA, and that leads to the VRSA," he said.

According to the Inquirer, the patient had MRSA when she was admitted to Pennsylvania Hospital and has been in isolation since her arrival.

As a precaution, staff members who have been in contact with the patient, are being tested and the Pennsylvania Department of Health and the Centers for Disease Control and Prevention have launched an investigation.

Click here to read more from The Philadelphia Inquirer.

Click here for more information on VRSA from the CDC.