Spread by the bite of infected Aedes mosquitoes, global infections of the disease number at least 240,000 this year.

Thousands of cases of the chikungunya virus, which sickens people bitten by an infected mosquito, have broken out in China during the past week. The virus causes extremely severe joint pain and fever,

China's chikungunya surge and expanding Aedes mosquitoes pose a low but growing risk of local transmission in California, scientists say.