Updated

U.S. syphilis cases climbed for the seventh straight year in 2007, and increases in the disease among gay men and blacks largely contributed, government researchers reported Wednesday.

The trend can be partly blamed on too few gay men getting recommended annual screenings for syphilis and other sexually transmitted diseases, the federal Centers for Disease Control and Prevention said, citing studies released at an STD conference in Chicago.

While the number of cases still is relatively low — 11,181 last year — the trend worries public health officials, who say better awareness and screening is needed.

About 60 percent of syphilis cases last year occurred in gay men, compared with just 5 percent in 1999, according to preliminary CDC data presented at the conference.

The main symptom is painless sores at the site where the syphilis bacteria entered the body. It is easily treated with antibiotics if caught early; if not, complications can include blindness and organ damage. Syphilis also increases susceptibility to AIDS infections, and can be fatal to infants who get it from infected mothers during pregnancy.

The data show the syphilis rate increased about 12 percent between 2006 and 2007, to about 3.7 cases per 100,000. That's a jump from 9,756 cases in 2006 to 11,181 last year, CDC researchers reported.

It's also a 76 percent increase since 2000, when the rate was 2.1 per 100,000.

Among black men, rates jumped 25 percent to almost 22 cases per 100,000. Among black women, there was a 12 percent increase, to about 5 cases per 100,000.