More than 7,000 cases have been reported to the authorities of the chikungunya virus, which can cause fever and joint pain.
The outbreak has been mostly across the city of Foshan, in the southern province of Guangdong, with the authorities tackling the rise in cases with methods last widely seen in China during COVID.
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Workers have been seen spraying clouds of disinfectant around streets, residential areas and office buildings where people may come into contact with the mosquitoes which are born in standing water.
People have been urged to use mosquito nets for beds and to apply insect repellent on exposed skin.
Young and older age groups, alongside those with pre-existing medical conditions, are said to be most at risk.
However, the number of new cases appears to be dropping slowly, according to authorities.
Heavy rains and high temperatures in China have worsened the outbreak, which is generally common in tropical areas but came on unusually strong this year.
One case of the virus has also been reported in Hong Kong.
Death from chikungunya is rare but joint pain can be severe and disabling and might persist for months.
