According to the World Health Organization (WHO), 5.6 billion people are at risk of arboviral diseases such as chikungunya. Other widespread arboviruses impacting humans include dengue, Zika and yellow fever. Symptoms of the disease include fever, joint pain and swelling, headache, muscle pain and rash, according to the CDC.

The chikungunya virus has rapidly spread to about 8,000 patients in just four weeks, mainly across China’s Guangdong province to the south, with the city of Foshan being hit the hardest, according to The New York Times.

U.S. health officials issued a warning to travelers about a mosquito-borne illness being transmitted in parts of southeast China.