Residents wade through debris along a flood-hit street after waters from a river overwhelmed towns following days of heavy rain in Huaiji County, south China's Guangdong Province, on June 19. (Deng Hua/Xinhua via AP, file)

TAIPEI, Taiwan — Chinese authorities are using nets, spraying insecticide and even deploying drones to fight the mosquito-borne chikungunya virus, which has infected thousands of people.

Authorities had reported more than 7,000 cases of the virus as of Wednesday, mostly in the southern Chinese manufacturing hub of Foshan, some 105 miles from Hong Kong. The number of new cases appears to be dropping slowly, according to authorities.

It appears to be the largest chikungunya outbreak ever documented in China, according to Cesar Lopez-Camacho of the University of Oxford. The virus is transmitted by infected mosquitoes and can cause fever and joint pain.

“What makes this event notable is that chikungunya has never been established in mainland China before,” Lopez-Camacho said in a statement. “This suggests that most of the population had no pre-existing immunity, making it easier for the virus to spread quickly.”

Chinese state television has shown workers spraying insecticide around city streets, residential areas, construction sites and other areas where people may come into contact with mosquitoes. Workers sprayed some places before entering office buildings.

Unusually heavy rains and high temperatures have worsened the crisis in China, and authorities are using drones to try to find standing water, where mosquitoes lay eggs.

Authorities also have threatened to fine people who don’t empty water from outdoor receptacles. Residents can be subject to fines of up to $1,400 and have their electricity cut off.

Because of the virus, the U.S. has issued a travel advisory suggesting that Americans take extra precautions when visiting China’s Guangdong province, where Foshan is located, as well as Bolivia and some island nations in the Indian Ocean.