More screenings may be the reason for an increase in the number of sexually transmitted diseases in 2011, particularly among men, says a report by the Centers for Disease Control and Prevention.

The annual all stds report, released in December 2012, shows more than 1.4 million chlamydia cases in 2011 — the largest number reported to the CDC for any condition — and an increase of 8% from 2010. From 2007 to 2011, the rate of chlamydia jumped 36% in men and 20% in women (cdc.gov/std/stats11/Surv2011.pdf).

"The continued increase in chlamydia case reports in 2011 most likely represents a continued increase in screening for this usually asymptomatic infection, expanded use of more sensitive tests and more complete national reporting, but it also may reflect a true increase in morbidity," study authors said in the report.

Gonorrhea and syphilis showed higher increases in men than women from 2010 to 2011. Gonorrhea rose 3% in women and 5% in men. Primary and secondary syphilis infection went up 4% in men but down 9% in women.

Better access to urine-based technology for chlamydia and gonorrhea is probably encouraging more men to be tested, said Arik V. Marcell, MD, MPH, an assistant professor in the Dept. of Pediatrics at Johns Hopkins University in Baltimore. These tests are more acceptable to men "rather than older swab collection techniques that were painful," he said.

Although syphilis cases reached historic lows in recent decades, the CDC report found men who have sex with men accounted for 72% of primary and secondary syphilis cases reported in 2011. Failing to obtain proper medical care is a likely contributor to the high numbers of syphilis infections in gay and bisexual men, said Hillard Weinstock, a medical epidemiologist in the CDC’s Division of STD Prevention.

"Risk behavior alone does not explain the disproportionate levels of infection among gay and bisexual men," Weinstock said. "Complex issues like homophobia and stigma also help fuel infection and can make it difficult for gay and bisexual men to seek appropriate care and treatment."

Americans ages 15 to 24 are at the highest risk for chlamydia, gonorrhea and syphilis, data show. Research finds that risky behavior, such as not wearing condoms, remains high among youths, Weinstock said.

"There is no one single explanation for the high levels of STD infections among youth," Weinstock said. "A complex combination of behavioral, biological and cultural factors place youth at a higher risk of acquiring STDs than adults."

Better patient assessments by primary care physicians can reduce the number of STDs, Dr. Marcell said. “Health care providers need to conduct comprehensive assessment with all patients, especially youth, for sexual behavior. This includes assessing for types of sexual activity; number of partners, including partner concurrency; use of contraception, including condoms;” and STD history.

Sexual health education also can be improved, he said.

"Promotion of sexual health and understanding of its consequences are critical for the nation, especially for young persons," he said. "This includes supporting comprehensive sex education in school and at home."