Across the board, sexually transmitted infections are on a “shocking” upward trajectory, according to public health experts. Preliminary data from 2021 that the Centers for Disease Control and Prevention released in September shows upticks in cases of gonorrhea and chlamydia — but outpacing them is a disease that the US at one point nearly succeeded in eliminating: syphilis.

Syphilis is a sometimes-fatal infection caused by a spiral-shaped bacterium that leads to skin rashes in its early stages and, in its later stages, complications ranging from neurologic problems to cardiovascular disease. About a quarter of people with a syphilis infection who don’t get treated have serious complications — including death in around 10 percent of cases.

Most concerning is the data on who is getting infected with syphilis: Case rates in women and babies rose almost threefold between 2017 and 2021 — a much larger increase than the rise among men, and larger still than the uptick in other sexually transmitted infections. In that time range, the number of syphilis cases in women rose from two per 100,000 people to seven per 100,000, and the number of infants born with congenital syphilis — not including those who died before birth — increased from 24 to 74 per 100,000.

The abrupt rise of the infection in women and babies ought to sound an alarm. When a baby has syphilis, it’s usually because it was infected while in the womb; about 40 percent of pregnancies in people with syphilis result in the death of the fetus or newborn. In the US, prenatal care involves syphilis testing, so delivering a baby while having untreated syphilis signals that the mother faced a barrier to getting prenatal care. When many people are delivering babies with congenital syphilis, it’s a sign that America’s health care system is failing women on a larger scale — especially women of color, who according to the data have the highest rates of infection.

To understand syphilis’s explosive rise — and why experts are worried about containing it — it’s helpful to understand the infection itself, the risks it poses, and the gaps in the US health care system that are allowing it to surge.

Syphilis is easy for both patients and providers to miss

It’s worth saying upfront that the early stages of syphilis are pretty easy to treat. A single shot of penicillin does the trick — and for people allergic to penicillin, two weeks of the cheap and widely available antibiotic doxycycline also works very well to clear the infection.

But if a syphilis infection isn’t interrupted by treatment, the disease usually progresses in three stages. The first begins with a single, painless bump that generally shows up a few weeks after infection. This bump is usually located where the bacteria that causes the infection first entered the body — usually in or around the mouth, genitals, or anus, but occasionally on other skin sites like the hands.

After three to six weeks, the bump goes away on its own, and within another few weeks, a more widespread rash shows up, often on the palms and the soles of the feet. This second stage can also include other symptoms that look a lot like the flu; fever, swollen lymph nodes, and sore throat aren’t uncommon. But whatever symptoms the person has, they also go away on their own, even if they don’t get treated.

Over the course of these first two stages and for about a year afterward, a person living with syphilis is contagious. Usually, the infection spreads through contact with a sore during sex, although it can also spread through kissing if a person has an oral sore. Pregnant people with syphilis infections can pass the infection on to their babies while they are in the womb.

Once the second stage is over, the infection goes into hiding in what experts call the “latent stage” of infection. This period, during which people have no signs of infection, can last for years or even decades.

In some people, latent syphilis infection might never cause another problem for them. But in others, it can reappear in a third stage of infection. At this point, it can affect multiple organ systems, causing a range of problems so diverse that the infection has earned the moniker “the Great Pretender”: It can cause brain disease that looks like psychosis, nerve disease that looks like stroke, eye disease that looks like conjunctivitis, and a variety of other problems.

Syphilis’s squirreliness means some people never realize they’re infected at all. “They don’t even know if it’s a problem because it doesn’t hurt, burn, or itch,” said Irene Stafford, an OB-GYN and syphilis researcher at the University of Texas Health Science Center at Houston.

In a recent review of records from 8.2 million blood donations in the UK, 316 donors tested positive for a past or current syphilis infection, and 60 percent of them were unaware of their infection.

It’s not just people with syphilis who often overlook infections: Health care providers miss the diagnosis with some regularity. According to a CDC spokesperson, among all the cases of syphilis in newborns the agency counted in 2021, 7 percent were born to mothers whose infections were undiagnosed despite getting timely maternal care.

That’s in part because so many providers don’t ask about patients’ sexual history, but it’s also because syphilis testing itself is notoriously pretty complicated. The best available tests only show whether a patient has ever had syphilis by measuring their level of antibodies against the bacteria. A provider might make a syphilis diagnosis in one visit if they find a characteristic rash during an exam — but otherwise, they have to repeat the test weeks to months later to determine whether the antibody level is rising or falling.

That means that even if a provider orders the right test and understands the result, they likely cannot make a diagnosis or treat the infection if a patient doesn’t come back for at least one more visit. This results in many missed opportunities for catching and treating infections — and many more opportunities for onward transmission of the disease. And it’s why routine health care, particularly during pregnancy, is so critical.

Health care guidelines recommend syphilis screening tests for people at high risk for either getting infected with syphilis or having severe consequences from an infection — including people with HIV infection and pregnant people, for whom testing is required in all but eight states.

Waning funding for sexual health and prenatal care clinics is contributing to rising congenital syphilis rates

In the year 2000, syphilis rates among Americans were at an all-time low, with 80 percent of the nation’s counties entirely syphilis-free. The disease largely affected men who had sex with men. The rates had dropped so low because of “massive behavior change due to the AIDS epidemic,” said Jeffrey Klausner, an infectious disease doctor specializing in HIV and STIs at the University of Southern California’s medical school. Many men in these communities responded to HIV’s devastation with widespread increases in condom use and decreases in numbers of sexual partners and group sex. That helped bring syphilis numbers down.

In absolute numbers, the majority of syphilis infections continue to occur among men who have sex with men. And while their infection rates have risen steadily since 2000, that uptick has been sluggish compared with the meteoric increases among women and babies.

Why are case numbers back up now? And why is syphilis affecting so many women? It’s likely due to the convergence of a few trends:

1. As treatment advances changed HIV from a death sentence into a chronic but manageable condition — and as HIV PrEP, medicine that reduces the risk of HIV infection, became more widely used among men’s sexual networks in the early 2010s — the urgency to use condoms faded. Meanwhile, sexual risk-taking increased as the internet simplified hookups. Some women have sex with members of these networks, increasing their risk for infection.
2. From 2004 onward, funding for dedicated STI clinics and public health in general began to drop, reducing access to sexual health services for low-income Americans in particular. “If you adjust for inflation, those funds have fallen by 41 percent over the past 20 years,” said Elizabeth Finley, who directs communications at the National Coalition of STD Directors.

“Those things come together and create the perfect conditions for rapid rises in sexually transmitted infections, and then spill over into populations like young women of reproductive age through their male partners,” said Klausner.

At the same time, the health care system is in a weaker position than ever to respond to the rising tide of infections, he said. State and local public health departments have few resources for testing and following up in pregnant women, and many clinicians — except those who specialize in men’s sexual health — are often unaware of syphilis’s resurgence and don’t know how to diagnose or treat it.

Catching more cases requires better prenatal care access and addressing other intersecting public health crises

The two trends above are made worse by a third: Prenatal care, which can catch infections, is becoming increasingly unavailable nationwide. Hospitals with birth centers have been closing at an astonishing rate, obstetricians have been leaving rural communities for urban centers, and in 2020, about 11 percent of American women were uninsured.

As the below March of Dimes map of US maternity care access in 2020 shows, these trends have disproportionately affected the South and the Plains states, leaving 7 million women of childbearing age with limited access to care (counties in yellow and orange, defined as having fewer than two birth centers and fewer than 60 OB-GYNs for every 100,000 births) or in an outright maternity care desert (counties in red, defined as having no birth centers or OB-GYNs).

It’s in these health care system fissures that syphilis has begun to claw its way back. The system intended to catch syphilis in pregnancy is failing, largely because the women at highest risk for infection aren’t getting prenatal care.

Although the epidemic has spread to nearly every state in the US, rates are highest across the South and in the West. Just eyeballing CDC data (compare the map below with the map above), you can see there’s a lot of overlap between regions that in 2020 had the highest rates of congenital syphilis and those with the least access to prenatal care.

It’s also easy to see how syphilis is impacting certain racial and ethnic groups more than others. In the last five years, congenital syphilis rates have increased precipitously among babies born to Native American, Pacific Islander, Hispanic/Latino, and Black Americans, due largely to a combination of rural strain and systemic racism, said Robert McDonald, a medical epidemiologist who works on syphilis prevention efforts at the CDC.

Sometimes pregnant people don’t get the care they need because the clinic is too far away — but other times, it’s because they’re afraid to.

For example, people with addiction disorders may avoid seeking prenatal care out of the legitimate fear they could be arrested for using drugs while pregnant, said McDonald.

Addiction disorders also increase the risk of getting infected with syphilis to begin with: According to a 2019 report, an increasing proportion of heterosexual syphilis transmission is associated with drug use, especially methamphetamine and heroin use.

In different parts of the country, the reasons pregnant women with syphilis don’t get prenatal care may be different, said McDonald. Substance use may be a particularly important barrier in rural areas and in Western states, while geographic distance from health care plays a larger role in the South, he said. In one of her studies, Stafford found pregnant women nationwide were more likely to fall out of syphilis care if they engaged in transactional sex or substance use, were experiencing homelessness, or had undiagnosed or untreated psychiatric illness.

So while improving funding for sexual health clinics and maternal care would help, it’s not enough to just make the care these places offer more geographically available across the board. The care also needs to be tailored to the specific reasons mothers aren’t seeking care, and must be bolstered with wraparound services aimed at reducing the health impacts of addiction disorders, homelessness, trafficking, and mental illness.

That’s a tall order in a country that can’t even agree that everyone has a right to basic health care services to begin with.

There’s still hope for reducing syphilis transmission

Covid-19 likely exacerbated the syphilis crisis because it required state and local public health officials to reassign most of their sexual health staff to pandemic-related roles, said Finley. It also led to abbreviated hours at many STI clinics, and resulted in many appointments taking place as telehealth visits — during which it’s more complicated to order the kind of lab work that would catch a syphilis case early. “We know that the pandemic played a role just because that failsafe failed,” she said.

So what can be done to rein in this alarming surge in covid cases?

A 2017 study suggested that in the sexual networks of men who have sex with men, using a single dose of doxycycline as post-exposure prophylaxis — sort of like a “morning after” pill — reduced syphilis cases by 73 percent. The CDC hasn’t yet issued guidance broadly recommending the practice, in part because it’s not yet clear what its impact could be on antibiotic-resistant “superbugs.” Still, sexual health experts think the strategy has enormous potential for reducing syphilis transmission in key communities, provided patients can overcome its side effects, which include gastrointestinal upset (i.e., bellyaches) and sun sensitivity.

“I do not think it’s a silver bullet — I do think it’s another tool in the toolkit,” said Philip Chan, a Brown University infectious disease doctor who directs the largest sexual health clinic in Rhode Island.

However, studies of so-called “doxy-PEP” haven’t yet included heterosexual women, and doxycycline isn’t safe for use in pregnancy. That means it will be some time before it has an impact on syphilis rates in women and infants.

Improving funding for STI clinics would also make a big difference, said Finley, who imagines federal dollars dedicated to sexual health care in the same way they are for HIV care and family planning. “The federal government has widely recognized and invested in clinical services as a part of their prevention and public health strategies, and we haven’t seen the same thing happen with STDs,” she said.

Another model for syphilis prevention already exists in the way most states now handle another sexually transmitted infection: HIV. The CDC recommends opt-out testing for HIV, which means patients in all health care settings are routinely tested for the infection unless they request not to be. Stafford doesn’t know of a national effort to make this happen for syphilis, although some states — like California — have rolled out their own campaigns to expand syphilis testing.

“We don’t have what HIV has,” said Stafford, “all these ads and all this money and all this media,” she said.

“This is an alarm,” she said. “Why are we not scared of syphilis?”