The Chinese mainland reported 491 confirmed monkeypox infections in July, compared with 106 cases in June, according to data released by the Chinese Center for Disease Control and Prevention on Wednesday.
No severe cases or related deaths had been reported since June, data shows.
The jump in infections in the past two months is a result of the stealth transmission of the virus among men who had sex with other men, active testing and reporting among high-risk groups and the increasing risk of imported cases from overseas, the China CDC said in a notice released on its official website.
According to the latest data, the 491 infections in July were scattered in 23 provincial-level regions.
In July, all cases were in males, and 96.3 percent of them were men who had sex with other men.
The risk of transmission through other channels was low, as none of the close contacts who were not involved in sexual contact with confirmed patients ended up getting infected.
The China CDC added that 89.2 percent of infections were detected when patients sought treatment on their own, and 6.5 percent were close contacts who were identified though screening and tracing efforts.
The remaining cases reported their infections on their own.
It said the majority of patients exhibited symptoms such as fever, herpes and swollen lymph nodes.
More efforts will be made to launch education campaigns among men who have sex with other men to rein in the outbreak, said the China CDC.
Measures will include setting up health promotion bulletins at pubs, clubs and bathing pools where people who are high risk often visit, and using social media platforms and mobilizing social organizations to spread disease prevention knowledge, it added.