The Department of Disease Control (DDC) said three people have already died from the mosquito-borne virus in the first three months of this year, compared to six fatalities in the whole of last year.
Dengue fever outbreaks usually occur about once every two years, so Thailand is due to be hit by a wave of the virus this year.
“We have not suffered a full-scale outbreak of dengue fever for two years, which means Thais are now at their lowest immunity against the disease,” explained DDC director-general Dr Opas Kankawinpong.
The DDC said cases of dengue fever would rise after the Songkran festival in April, driven by dengue type-2, a dangerous variant that causes severe symptoms and a high mortality rate.
“The initial symptoms of dengue fever are similar to those of Covid-19,” said Opas. “Now that Covid-19 is spreading in all regions of Thailand, it may be hard for patients and health professionals to differentiate between the two diseases.
“If you have high fever, runny nose, sore throat, or muscle aches, please see a doctor to get a blood test for dengue fever. Many people with these symptoms think that they have Covid-19 and therefore only get the coronavirus test,” he said.
A patient can have both Covid-19 and dengue fever at the same time, and both diseases can be found in all age groups, he added.
Opas said most Covid-19 patients will eventually develop respiratory symptoms, while dengue patients will often lose their appetite and feel nauseous as the disease progresses.
The DDC advised people to use mosquito nets and rid their properties of any rainwater trapped in puddles or containers to reduce the chance of being bitten by dengue-infected mosquitos.