The number of St. Clair County residents diagnosed with a sexually transmitted disease dropped markedly in the past year, but health officials worry that may just be because fewer people are seeking treatment.

The county has consistently ranked in the top five in the state of people diagnosed with sexually transmitted diseases, or STDs. Yet this past year saw the number of cases drop 31 percent for chlamydia and 35 percent for gonorrhea.

While health officials are hopeful the statistics are true, they are concerned the numbers merely reflect less reporting of the cases.

The symptoms of the diseases may go away after a couple days and some people refuse to see a doctor, according to St. Clair County Director of Health Protection Barbara Hohlt. The disease lingers, though, after the symptoms go away.

"The statistics are based on diagnosis, which is very misleading since so many people don't seek treatment," Hohlt said.

New cases of chlamydia in the county dropped from 2,011 people in 2011 to 1,382 in 2012. Likewise, gonorrhea cases decreased from 664 to 428 and syphilis decreased from 13 to four cases in the same time span.

The statistics are considered provisional until approved by the Illinois Department of Public Health. The actual number of new cases is anticipated to be higher than reported, Hohlt said.

Excluding Cook County, the county ranked first in the number of reported cases of gonorrhea, second in chlamydia and third in early syphilis in 2011. Cook County has 5.2 million residents compared with St. Clair County's 270,000 residents.

In comparison, Madison County ranked eighth in gonorrhea, ninth in chlamydia and 10th in syphilis in 2011. Reported cases of chlamydia and gonorrhea in Madison County dropped slightly in 2012.

New cases of chlamydia in Madison County dropped from 1,058 in 2011 to 1,011 in 2012. Reported cases of gonorrhea decreased 19 percent, from 201 in 2011 to 163 in 2012. And the reported cases of early syphilis actually jumped from five to 10 year over year.

Along with traditional care, the county is able to help patients through a practice called "expedited partner therapy," according to the county's Manager of Infectious Disease Prevention Services Marsha Wild. The practice allows doctors to provide prescriptions or medications to the patient to take to their sexual partners without a medical provider examining the partner.

Sexually transmitted diseases also increase the chance of problems with fertility and infant mortality, Wild said.

Contact reporter Daniel Kelley at dkelley@bnd.com or 618-239-2501.