One of the nation’s most common forms of sexually transmitted diseases has fallen to its lowest level ever recorded, but there’s still improvement needed, according to a new government report out Monday.

The report, part of the Centers for Disease Control and Prevention’s annual report card on sexually transmitted diseases (STDs), found that gonorrhea rates in 2009 – the most recent year for which figures are available – were at their lowest level since 1941. The report also found that syphilis rates among women held steady after several years of increases. But the nation’s chlamydia cases were up 19 percent.

The CDC said that while overall the findings are encouraging, “there are large disparities in STD rates by race and age. Some racial/ethnic minority groups have much higher STD rates than whites, and young African Americans are particularly hard-hit.”

Syphilis rates among young black men were about double the rate they were in 2005, the CDC found. Chlamydia rates reached a record high in 2009, which the CDC said probably represents increased testing for the disease.

Gonorrhea infections in 2009 dropped to about 111 cases per 100,000 population, down 10.5 percent from 2008, The 2009 rate, the third consecutive annual decline, was the lowest since record-keeping began in 1941.

A single test can screen for gonorrhea and chlamydia. in 2000, a quarter of women 25 and under were tested for chlamydia, compared with nearly half in 2009.

Once diagnosed, all three reportable STDs are easily treated with antibiotics, said Charlotte Kent, acting director of the CDC’s Division of STD Prevention. although gonorrhea causes symptoms, chlamydia is likely not to, so testing is critical, she said.

“Undiagnosed chlamydia and gonorrhea are preventable causes of infertility,” Kent said.

The overall syphilis rate has risen every year since 2001, mostly in men but, more recently, in women. in 2009, there were 4.6 cases per 100,000 population, a 59 percent jump since 2005.

Jeanne Marrazzo, president of the American Sexually Transmitted Disease Association, called the syphilis rate “alarming.”

Rates of all three STDs are higher in blacks than whites, Kent noted. “We’ve seen some definite signs of progress, but we still see these disparities exist,” she said.

The 2009 syphilis rate in blacks was nine times that of whites; in 1999, the difference was 24-fold.

“It’s not an issue of behavior,” Kent said, but one related to the fact that the three STDs are more common in blacks.