Atlanta ? Sexually spread diseases — for years on the decline — are on the rise, with reported chlamydia cases setting a record, government health officials said Tuesday.

The increase in chlamydia, a sometimes symptomless infection that can lead to infertility in women, is likely because of better screening, experts said. In 2007, there were 1.1 million cases, the most ever reported, said officials at the Centers for Disease Control and Prevention.

At least 15,000 women become infertile each year because of untreated chlamydia and gonorrhea infections, said Dr. John M. Douglas Jr., director of the CDC’s Division of STD Prevention.

Syphilis cases, which number only in the thousands, also rose modestly, while the number of gonorrhea cases remained roughly the same. Syphilis can kill, if left untreated, but chlamydia and gonorrhea are not life-threatening.