“Condoms cannot stop it” syphilis fears···Why did the Korea Disease Control and Prevention Agency put the brakes on worries about ‘a surge’? - 경향신문

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A palm rash, a representative symptom of secondary syphilis. AI-generated image

“Even condoms cannot stop it.” “It spreads even with just a kiss.” “The return of syphilis we thought had disappeared.”

These were this week’s torrent of headlines about syphilis. Domestic syphilis reports rose from 401 in 2022 to 2,790 in 2024, a sevenfold increase in two years, and in Seoul syphilis ranked first with 39 out of 83 cases of imported infectious diseases. On top of this came news that syphilis patients in nearby Japan had topped 10,000. With multiple statistics and overseas outbreak reports overlapping, it was enough to give the impression that syphilis is being brought in from abroad and spreading domestically.

According to the government on the 21st, as anxiety over a syphilis outbreak spread, the Korea Disease Control and Prevention Agency took the unusual step of issuing an explanatory press note on the evening of the 19th to calm the situation. Aiming at analyses claiming a surge in patients, it drew a clear line, saying “Simple statistical comparison is not possible.” What the Agency took issue with was placing numbers tallied under different criteria side by side and interpreting them as “a sevenfold surge in two years.”

In fact, this is not the first time the Korea Disease Control and Prevention Agency has issued such an explanation about syphilis. The same misunderstanding and the same clarification were repeated in 2024 and again last year. So why does this keep happening? Is domestic syphilis really increasing? How far is the claim that even using a condom cannot stop it accurate?

There has been no shortage of figures surrounding syphilis, but how those figures are produced under which criteria has not been fully explained. Based on the Agency’s explanation and the published statistics, we looked into it.

Q. Is it true that the number of syphilis cases in Korea ‘increased sevenfold in two years’?

The figures 401 in 2022 and 2,790 in 2024 are themselves correct. Arithmetically, going from 401 to 2,790 is about sevenfold. The problem is that the two figures were not counted using the same criteria.

In 2022, reports of syphilis cases came from sentinel surveillance sites designated by the Korea Disease Control and Prevention Agency. The reportable stages were limited to three types: primary, secondary, and congenital syphilis. Starting in 2024, however, the system changed to comprehensive surveillance in which all medical institutions nationwide report syphilis cases. The reportable stages were also expanded to add tertiary syphilis and early latent syphilis to the existing three. In other words, the number of reporting facilities increased significantly, and the scope of what is counted widened.

In fact, among the 2,790 cases in 2024, early latent syphilis accounted for 1,220 and tertiary syphilis for 51. A total of 1,271 cases, or 45.6% of the whole, were stages newly included as reportable from 2024. This is why the Agency stated that “Simple statistical comparison of reports during the sentinel-surveillance period (20202023) with post-2024 reports is not possible.”

Q. Why did the method of counting syphilis cases change like this?

The syphilis surveillance system conducted comprehensive reporting through 2019, switched to sentinel surveillance for 20202023, and returned to comprehensive reporting in 2024. The Korea Disease Control and Prevention Agency explains this as a measure to “find more.” With syphilis increasing in many countries overseas, surveillance was strengthened to proactively grasp the scale of domestic occurrence.

It is not that the possibility of the figures looking larger because of this was unforeseen. According to an Agency official, when the surveillance system was changed in 2024, concerns were raised within the medical community that “If early latent syphilis is also made reportable, it could look as if syphilis has suddenly become much more common in Korea.” In the end, the improved system, designed to monitor syphilis more closely, has become the background for annual debates about “an explosion in cases.”

Q. Then is syphilis in Korea actually increasing or decreasing?

To gauge a trend, you have to compare using the same yardstick. We aligned the reportable stages for 2019 and 2024, when the Agency conducted comprehensive surveillance, to primary, secondary, and congenital syphilis and compared them. Reports decreased from 1,753 in 2019 to 1,519 in 2024, down 13.3%. For 2025, the figure was 1,182, 32.6% lower than 2019.

The reporting system and the reportable stages were the same in 2024 and last year. Total reports decreased about 20.8%, from 2,790 in 2024 to 2,211 last year. An Agency official said, “Judging by the simple trend, cases should be seen as decreasing,” adding, “Claims and billing data from the National Health Insurance system also show a declining tendency.”

What about this year? Looking at the weekly reporting trend that the Agency publishes, 1,288 syphilis cases were reported from January through August 18. However, this is not final. After receiving a full year of reports, the Agency reviews epidemiological investigation forms to classify stages and remove duplicates. Even after closing at year’s end, this takes another two to three months. In short, it is too soon to set this year’s 1,288 alongside last year’s finalized 2,211 and compare them. Based on the numbers currently available, there is no basis to say syphilis in Korea “surged sevenfold in two years.”

Q. If ‘syphilis ranks first among imported infectious diseases in Seoul,’ is it mainly contracted overseas?

“39 out of 83” means syphilis was the most common when looking only at imported infectious diseases confirmed in Seoul this year. It is not a figure that calculates the proportion of overseas-acquired infections among all syphilis cases in Korea.

According to “Epidemiologic Characteristics of Syphilis in 2024,” published in the Agency’s journal ‘Weekly Health and Diseases,’ 117 people out of a total of 2,790 syphilis cases4.2%were presumed to have been infected abroad. The presumed countries of infection were the Philippines (22), Laos (19), and Thailand (14), in that order. Japan was fourth with 13. The Agency’s researchers analyzed that the presumed route of infection was mostly domestic.

“Syphilis is the most common among imported infectious diseases” and “Most syphilis patients were infected overseas” are different statements. Given the recent increase in cases in Japan, it is necessary to keep an eye on the possibility of importation, but there is no evidence at present to attribute domestic syphilis occurrence primarily to overseas travel.

Q. Who is mainly affected in Korea? Is it already spreading in the community?

In the finalized 2024 data, men accounted for 2,177 cases, or 78.0% of infections. By age, people in their 20s were 853 (30.6%) and those in their 30s were 783 (28.1%), so those in their 20s and 30s made up more than half. Although the Seoul metropolitan area had the most reports at 1,631 (58.5%), the difference with other regions was not large when comparing incidence per 100,000 people: 5.9 in the capital region.

That does not mean syphilis affects only certain genders or age groups. Because syphilis is mainly transmitted through sexual contact with an infected person, anyone who is sexually active can become infected. The current domestic statistics simply indicate that men in their 20s and 30s are being identified relatively more often.

The Agency’s answer regarding community spread was relatively firm: “We are not at that stage.” Since syphilis is primarily spread via sexual contact, it differs in nature from infections like the common cold or COVID-19 that spread collectively to unspecified people through everyday contact.

Q. Is the claim that “syphilis cannot be prevented even with a condom” true?

An official at the Korea Disease Control and Prevention Agency said, “If a condom is used properly, transmission can be prevented.” There are, however, exceptionssuch as when a condom tears or slips off during sex. Syphilitic lesions can also occur not only on the genitals but around the anus, on the lips, and in the mouthareas a condom does not cover. Direct contact with such lesions can result in infection even when a condom is used.

Q. Then can it spread through everyday contact like kissing, toilets, towels, or public baths?

According to the Agency, there have been no reported cases of infection through everyday contact alone. Although the syphilis bacterium can survive outside the body for a certain time under specific conditions, it is not transmitted by contact at the level of saliva droplets. The same applies to toilets, towels, tableware, public baths, and swimming pools.

There are, however, exceptions. Primary syphilis presents symptoms around the genitals, but secondary syphilis causes a body-wide rash. If blisters formed at this stage rupture and the fluid touches an open wound on another person, transmission can occur.

Also, the expression “It spreads even with just a kiss” is inaccurate. For transmission via kissing or oral sex, specific conditions must be met, such as cuts on the skin or mucosa, or the partner being in a period of high bacterial shedding. It is not an infection that spreads through a light peck when such conditions are not present.

Q. Can you have syphilis with no symptoms at all? When should you get tested?

Yes. The most common stage reported in 2024 was early latent syphilis, which means there were no outward symptoms at the time of diagnosis. Last year as well, early latent syphilis accounted for 979 cases, or 44.3%.

The problem is that such infections are often not detected in routine health checkups. A dedicated test is needed to confirm syphilis infection. Timing also matters. Antigen testing with PCR can be done two to three days after a risky contact, but the cost can be burdensome. Antibody testing requires at least three weeks before it can confirm positivity. A negative result immediately after exposure is therefore not grounds for reassurance.

Pregnant women need to be especially careful. Although prenatal screening includes syphilis, there were 12 congenital syphilis cases in both 2024 and last year. An Agency official cited reasons such as testing at a time when antibodies had not yet appeared and failure to complete treatment, for example by using agents other than penicillin. It is not enough to have been tested; you must confirm when the test was done and whether treatment was completed perfectly.

Fortunately, syphilis is a treatable infection. Primary, secondary, and early latent syphilis can be treated with a single intramuscular dose of benzathine penicillin. If the timing is missed, the approach changes: late latent or tertiary syphilis requires weekly penicillin injections for three weeks, and suspected neurosyphilis requires hospitalization for intravenous therapy. Treatment does not confer immunity, so reinfection can occur upon later exposure.