Syphilis is quietly reappearing in parts of Kenya even as more people get tested than ever before, revealing a health problem that is still spreading in pockets of high movement and low screening coverage.
New national data shows that while infections appear to be dropping overall, several counties are now recording fresh increases, with cities and transport corridors carrying the heaviest load.
Figures from the National Syndemic Disease Control Council show a steady rise in screening across the country. In 2020, health workers tested 1.29 million people. By last year, the number had gone up to 1.42 million, showing growing access to testing services in public facilities.
With more testing, health teams have been able to identify infections that were previously going unnoticed. In 2020, about 16,000 people tested positive for syphilis.
By 2025, the number had fallen to just above 9,000 cases, a drop of more than 40 per cent. Health officials link this change to wider screening, more reporting facilities, and improved detection systems, with the national positivity rate now at its lowest level recorded.
Even with the overall decline, the report shows that 15 counties are still reporting high numbers or new increases. Health experts point to population movement in urban areas, weak tracking of cases, and irregular supply of testing kits as some of the factors allowing the infection to continue spreading in certain regions.
Nairobi remains the most affected county. It recorded over 1,000 cases in total. In 2023, there were 961 positive cases, and by 2025 the number had increased to 1,068 out of 161,020 people tested.
“Nairobi is a massive urban transit hub where thousands of people constantly move in and out for work, business, and travel, the virus is finding a steady stream of new pathways to spread,” says the report.
Homa Bay presents a different pattern, with fewer tests but a higher rate of infection. In 2025, 37,348 people were screened and 508 tested positive, giving a positivity rate of 1.4 per cent.
Health officials say this shows the infection remains firmly established in the county despite ongoing screening efforts.
In Uasin Gishu, the number of positive cases rose sharply from 105 in 2023 to 152 in 2024, before climbing to 489 in 2025. Machakos also recorded a similar rise, moving from 62 cases in 2024 to 157 in 2025.
Surveillance teams have now flagged both counties as areas where the infection is re-emerging after a short period of lower numbers.
Health specialists say the trend of low figures followed by sudden increases points to silent spread in communities that were not fully reached by testing services. They warn that gaps in surveillance may be allowing infections to persist unnoticed until they show up in larger numbers.
The biggest concern remains the impact on pregnant women and newborns. When untreated, syphilis can pass from mother to child, leading to stillbirth, newborn deaths, or serious complications at birth.
In Nakuru County, targeted maternal screening highlights the risk. In 2024, 309 pregnant women tested positive, down from 474 the previous year, but still a worrying figure for health officials who say monitoring gaps continue to affect full tracking of infections.
Public health experts say two groups remain most exposed. These are people with multiple sexual partners and pregnant women who miss antenatal visits, often due to distance to facilities, stigma, or lack of testing kits when they seek care.