Hundreds of thousands of cases of chlamydia go undiagnosed each year, research by the Centers for Disease Control and Prevention suggests.
The study was conducted through the United States National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention.
Scientists' calculations were formulated by analyzing the information provided within the National Health and Nutrition Examination Survey (NHANES) from 2007 through 2012.
This study involved about 5,000 subjects from across American annually and included both children and adults.
Researchers found that 1.7 percent of men and women ages 14-39 have chlamydia, which works out to about 1.8 million infections each year in the United States.
There are 1.4 million cases reported to the CDC each year. As a reportable disease, all diagnoses of chlamydia are supposed to be reported to the CDC. That discrepancy signifies that as many as 400,000 cases of chlamydia not only go unreported, but likely go undiagnosed every year.
A major reason why chlamydia is so often undiagnosed is that it often produces no symptoms. Unlike other STDs which result in the appearance of symptoms within a matter of days after infection, chlamydia does not. And when symptoms do appear, they may be mild and resolve quickly.
Symptoms can include abnormal discharge from the penis or vagina, a burning sensation during urination, and pain or swelling in the testicles for men.
Along with the revelation of under-reported cases, they also found that young women are at a much greater risk of harboring chlamydia.
The investigators found that the chlamydia infection rate is highest among sexually active girls aged 14-19, at 6.4 percent, HealthDay News reported. The rate among sexually active boys aged 14-19 is 2.4 percent.
Among these female adolescents, chlamydia infection is nearly six times more common in African-Americans than in their white counterparts. The rate found among the African-American girls was 18.6 percent, while the teenage white girls had a much lower rate of 3.2 percent.