NEW YORK (AP) – Two New York men have been diagnosed with a rare sexually transmitted disease that can scar the genitals and is of the same strain recently found in Europe, the health commissioner said Wednesday.

Lymphogranuloma venereum, or LGV, is a form of chlamydia that also can damage the bowels and scar the anus. Among the six patients identified in the United States most also had the AIDS virus, health department Commissioner Thomas Frieden said at a news conference.

“We know LGV increases the risk of the spread of HIV because it causes ulcers and bleeding,” he said.

In the past New York had a few cases reported in males and females, but those were never laboratory confirmed, health officials said. The recent two cases in New York have been laboratory confirmed as LGV and are consistent with the pattern of LGV being found in men who had sex with other men, health officials said.

Frieden said the federal Centers for Disease Control and Prevention confirmed three LGV cases in San Francisco and one in Atlanta. He said gay and bisexual men were urged to abstain from sex or limit their number of sex partners and use condoms.

Unprotected anal intercourse is the key risk factor for the spread of LGV, which is difficult to diagnose.

Symptoms include painful bloody rectal infection that may be confused with inflammatory bowel disease. The first symptom may be a painless pimple or lesion on the genitals.

The onset of symptoms varies widely, health officials said. The initial lesion may appear from three to 30 days after exposure. An individual remains infectious as long as there are active lesions.

If identified early LGV can be treated with antibiotics. Untreated, it can cause permanent damage to the bowels and swelling and scarring of the genitals. Death is rare.

Dr. Susan Blank, New York’s assistant commissioner for sexually transmitted disease control, said the health department was treating the two cases as an “outbreak” in an aggressive effort to prevent the spread of what she called “a bad disease.”

An alert has been sent to physicians in New York. It encourages doctors, particularly those who care for HIV-infected or gay patients, to think about LGV if there are symptoms consistent with it, Frieden said.

Physicians were being asked to report suspected cases to the health department so it can help in diagnostic testing. The CDC will be notified of confirmed cases.

The president of the Latino Coalition on AIDS, Dennis DeLeon, urged gay men to be diligent about screening for sexually transmitted diseases.

“It sounds like a tired message, practice safe sex, but this is a disease that can leave permanent scarring on the anus,” DeLeon said. “Gay men should be asking their doctors about this.”

In the past two decades LGV has been uncommon in industrialized nations and primarily has been found in the tropics.

But in November, the National Institute for Public Health in the Netherlands said 92 cases of LGV among gay and bisexual men had been reported there over the preceding year, compared to the usual two or three cases a year. Frieden said cases also have been found in the United Kingdom.