A decade ago, this week, scientists at the University of Texas Health Science Center at Houston and the Institute for Genomic Research announced they had decoded the genetic information inside Treponema pallidum, the bacterium that causes the sexually transmitted disease (STD) syphilis.

At the time, Penelope Hitchcock, the chief of the sexually transmitted disease branch of the National Institute of Allergy and Infectious Diseases (NIAID), hailed the work as critical to developing better drugs. NIAID director Anthony Fauci added the genome would boost efforts to develop a preventative vaccine.

Syphilis wouldn't have us to kick around anymore. Right?

Flash forward one decade: There are no new wonder drugs—penicillin injections are still the primary treatment and cure of the rarely fatal illness. Meanwhile, the rate of reported cases of syphilis in the U.S. rose for the seventh consecutive year—up 12 percent between 2006 and 2007—according to preliminary data gathered by the U.S. Centers for Disease Control and Prevention (CDC).

Incidence is up among women, African-Americans and, most prominently, gay men, who account for 64 percent of the more than 12,000 people diagnosed last year with either primary or secondary syphilis infections. Primary infections appear as ulcers or shankers on the genitals, anus or mouth; secondary infections result in rashes on the foot's sole or the palm of the hand as well as hair loss and lesions on or around the genitalia.

ScientificAmerican.com caught up with medical epidemiologist Hillard Weinstock of the CDC to chat about the decade since the sequencing of the syphilis genome to try to figure out why we haven't tamed this STD.

When you hear that scientists have cracked the genome of a bacteria or virus, you assume that in the years to come there will be significant progress preventing or treating a disease. But, that's not what the numbers on syphilis indicate, correct?

We are doing much better than we were doing in 1990. We have seen increases in the last seven years, but even the number of cases of primary and secondary syphilis that we see today—approximately 11,000 reported cases, which is an increase from [the year] 2000—is still many times better than what we saw in 1990 when cases were over 50,000.

We really saw dramatic improvements and decreases in syphilis among men, among women, among all groups, through the 1990s. In 2000 the number of reported cases reached a nadir, [just over 6,000 reported cases]. We haven't seen that few cases reported in the history of reporting syphilis since the 1940s. We need to remember that in historical context, the number of syphilis cases we see today is relatively low.

However, we are concerned about the increase we've seen over the past seven years, predominantly in men who have sex with men. Since 2000, we've seen approximately a 76 percent increase in syphilis rates. And over the past couple of years we've seen some increases also in women and African-Americans—both groups in which we saw dramatic decreases in the 1990s.

Why are syphilis cases climbing? Overall HIV infection rates, which also decreased in the 1990s, seem to be holding steady or slightly declining. (Fewer than 37,000 people were diagnosed with HIV in 2006.)

A number of surveys have shown that some men who have with men are co-infected with HIV; depending on the survey you look at, it's anywhere from 20 to 70 percent. There are concerns that prevention fatigue may be playing a role—older gay men may no longer be hearing the prevention messages that they've heard for so many years. They become inured to them. There's also a concern of substance abuse, which might be playing a role—the epidemic of methamphetamine use, in particular.

Also, the successes of HIV treatment that allow individuals who are HIV-infected to continue to have an active life—and an active sex life, in particular—have contributed to some of this. I think there are probably a number of factors that might be playing a role in these increases.

1 Comments

1. 1. pu 01:48 PM 7/19/08

   The genome sequence by itself doesn't help much to design new drugs. One has to understand the function and interactions of the proteins which are almost always the targets of drugs. However, only the complete genome sequence made it possible to investigate all the interactions among Treponema proteins. We published this analysis just 2 months ago (Titz et al. PLOS ONE 3[5]:e2292). The next step would be to investigate the available set of interactions for potential drug targets. So, there is progress, even if it is not as fast as one would wish.

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