Thailand has seen an alarming rise in dengue fever cases, with more than 19,000 infections recorded since Jan 1 and 17 deaths, deputy government spokeswoman Traisuree Taisaranakul said.
The infection rate was at least 4.2 times higher than the number for last year.
Around 900 infections and one death were being recorded on average each week, with most cases found in Bangkok, Trat, Nan, Chanthaburi, Rayong and Mae Hong Son, respectively.
Children aged 5-14 were the worst-hit age group, followed by young people aged between 15-24, she said.
Dr Thares Krasanairawiwong, director-general of the Department of Disease Control, put the total number of infections so far this year at 19,503.
Anyone who thinks they may be infected should seek medical advice and avoid taking non-steroidal anti-inflammatory drugs such as aspirin and ibuprofen, Dr Thares added.