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.


With all these populations where syphilis incidence is on the rise, are there geographical patterns that you can see?

In men who have sex with men, we've seen increases throughout the country both in the [U.S.] west, in the South, in the Midwest, and east and Northeast. In heterosexuals, particularly in women—African-American women, more specifically—the increases that we've seen have been limited to the South. We're concerned that this might spread to other regions of the country, but for now, they're limited to the southern parts of the United States.


Any ideas why incidence is on the rise in the South? Poor quality of sexual education, maybe?

We don't have all the answers to that. We've always seen higher prevalence of syphilis in the South. It's not surprising that when there are increases that we would see them first in that region. The South is where we saw some of the biggest gains in syphilis control in the '90s.


What is the public health community doing to curb these increases?

CDC is working actively to promote better linkages between HIV and STD prevention programs nationwide. We're offering more STD testing at HIV testing sites. We're funding innovative STD prevention sites on the Internet, which is where many men who have sex with men, for example, meet partners [as well as] programs at bathhouses and other kinds of venues where men who have sex with men may meet and gather.


Everyone around the age of 30 or older has a pretty keen understanding of how the world became aware of HIV/AIDS in the 1980s. Does syphilis have a similar backstory?

At one time, syphilis, like HIV, was not treatable. Before the advent of penicillin, many more tens of thousands of Americans had syphilis. If you go back to the 1940s, almost 100,000 cases of primary and secondary syphilis were reported to the CDC at that time. So it was, at one time, the AIDS of its day—before antibiotics were developed and it became a very treatable disease. But, nevertheless, it is still associated with severe sequela and also associated with increased transmission and acquisition of HIV.


Is the perception, that relative to HIV/AIDS syphilis isn't something to worry about, a big hurdle for public health officials?

I think that is a challenge, constantly reminding the sexually active individuals, adolescents and even older persons—as well as health care providers—that this is still a problem, that this is still to be reckoned with and addressed. Gay men, for example, who are sexually active need to be tested for syphilis and other sexually transmitted diseases on a regular basis. Health care providers need to have a high level of suspicion in their patients that are sexually active for this disease.