The numbers of syphilis and chlamydia cases in the United States both went up in 2006, health officials from the Centers for Disease Control and Prevention said Tuesday. In a new report, the government tallied up more than a million cases of chlamydia, about 360,000 of gonorrhea, 37,000 of syphilis, and just 33 of chancroid. But it didn't keep tabs on genital herpes or human papillomavirus, which constitute many of the estimated 19 million new cases of sexually transmitted diseases that occur each year. Why don't we keep track of those, too?
There aren't any good ways to diagnose and treat them. To track a disease nationwide takes a lot of resources, and the government won't make that investment without a good reason. If counting cases can help doctors reduce the prevalence of a dangerous disease, then it's clearly worth the effort. But for genital herpes or HPV, there's no cure and no certain way to show how much the diseases are spreading. (The CDC's numbers come from state departments of health, which decide what to track based on recommendations from the Council of State and Territorial Epidemiologists.)
Any data the government could gather on genital herpes and HPV cases would be incomplete. Most people who are infected don't even realize that they have the diseases, so there's no way for doctors to diagnose them. Almost one in five adults has herpes simplex type two, which is responsible for most genital herpes infections, but only an estimated 10 percent of those people ever recognize their symptoms and seek medical help. HPV is extremely common but usually doesn't cause any symptoms at all.
When doctors do make a diagnosis, they're sometimes wrong. Blood tests for genital herpes turn up false positives with alarming regularity. In a population where 15 percent of people are infected, a positive test result may be correct 85 percent of the time. And a test for HPV in women has been commercially available for about a decade, but there still isn't a test approved for men.
Then there's the question of whether our government should gather numbers about genital herpes and HPV if the data can't help doctors treat more patients. Almost all HPV infections, for instance, go away on their own; about 5 percent of cases lead to genital warts or cancer. That helps explain why the HPV test is recommended only for a subset of the population: certain women who have had abnormal—but not extremely abnormal—Pap test results. As for genital herpes, today's best treatments aim to suppress, not cure, the infection.
Syphilis, gonorrhea, and chancroid, on the other hand, are relatively easy to diagnose and treat; CDC data on the diseases go back to 1941. Patients with these STDs have easily identifiable symptoms like skin lesions and rashes, and doctors can often confirm the diagnosis during the course of an office exam or by growing a culture. States only started to accumulate data on chlamydia after scientists developed a reliable test for the disease in the 1980s. It joined the official list of nationally reported STDs in the 1990s, pushed by a congressionally funded program to prevent infertility. (The CDC also used to tabulate figures for granuloma inguinale and lymphogranuloma venereum, STDs that caused genital ulcers.)
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Explainer thanks Matthew Golden of the STD Control Program for Public Health in Seattle and King County, Samuel Groseclose of the CDC, Peter Leone of the University of North Carolina at Chapel Hill, and Richard Rothenberg of Emory University.