PORTLAND — The Portland area is experiencing a dramatic rise in the number of gonorrhea cases transmitted by men having sex with other men.

Last year, the Maine Department of Human Services reported 11 cases statewide of male-to-male transmitted gonorrhea, with four cases in the greater Portland area. So far this year, there have been 11 cases, with 10 of them in Portland.

Dr. Dora Mills, director of the department’s Bureau of Health, described the numbers as “quite small.”

“However, whenever we detect cases of a sexually transmitted disease clustered in one area and in one population group, we become concerned about the potential for the disease to spread rapidly,” Mills said.

The increase has spurred state officials to ask southern Maine health care providers to be extra vigilant for gonorrhea among people at a high risk for contracting a sexually transmitted disease.

In addition, people who practice risky sex are being encouraged to get tested.

Gonorrhea can cause complications if not treated, including infertility, ectopic pregnancy and pelvic inflammatory disease. It’s estimated 40 percent of people who have the disease may not exhibit any symptoms.

Gonorrhea can easily be treated with antibiotics.

State health officials were at a loss to pinpoint the cause of the Portland increase.