Dr Manoon Leechawengwongs, a respiratory and critical care specialist at Bangkok’s Vichaiyut Hospital, went online to warn Bangkok residents that the chikungunya virus, spread through the bite of an infected Aedes mosquito, has mutated allowing one mosquito to be the carrier of both chikungunya and dengue viruses.

More than 500 people have been infected with the Chikungunya virus in Thailand’s southern provinces this year, a senior public health official said Monday.