Ross County recorded 180 cases of chlamydia in 2009, the most for any communicable disease that year but a slight decline from 191 cases in 2008, health officials said recently.

"The bacteria that causes chlamydia infects the cervix and urethra, and the symptoms it causes are sometimes so mild they go unnoticed, especially in men," said Helen Ricketts, the infectious-disease nurse for Ross County Health District. "But in women, over time the infection can spread to the fallopian tubes, causing serious damage to the reproductive organs." The STD also potentially can cause pelvic pain, she added.

Last year, the county had 80 cases of hepatitis C, down from 135 in 2008, according to data in a forthcoming report. In addition, the county saw 46 cases of gonorrhea last year. Neither chlamydia, gonorrhea nor hepatitis C is vaccine-preventable, noted officials.

In a trend she called "both scary and sad," Kathy Wakefield, the district's director of nursing, said cases of pertussis, or whooping cough, jumped from seven in 2008 to 26 in 2009. "There is a vaccine, but many parents are choosing to not have their children vaccinated," she said, adding that given the decline in vaccination, adults who are around children should consider having booster shots for vaccines that weaken over time.