More than 10,000 people in Japan have contracted syphilis this year, a level reached for the first time since comparable data became available in 1999, according to a preliminary report by the National Institute of Infectious Diseases on Tuesday.

The record surge in cases, which has generally trended upward from around 1,000 in 2013 and 2014 to a then record-high of under 8,000 in 2021 and the latest 10,141 figure, is thought to be partly due to increasing social media and dating apps usage facilitating meetings and sexual encounters with numerous partners.

While other factors cited as cause for concern had included the effects of the pathogen coming from abroad, syphilis cases had kept rising even when Japan had strict coronavirus pandemic rules on border entries. The results suggest, therefore, that infections are very likely to have spread due to domestic sexual activity.