The number of dengue fever cases is spiking in Indonesia, health officials said Monday, as the country battles to stem the spread of the new coronavirus.

Indonesia has had about 68,000 cases of the mosquito-borne viral infection since January, with at least 349 fatal cases, according to Siti Nadia Tarmizi, director of vector-transmission and zoonotic disease prevention and control at the Ministry of Health.

Supplied photo shows an Asian tiger mosquito. (Photo courtesy of U.S. Centers for Disease Control and Prevention)(Kyodo)

The spike in dengue fever cases has baffled officials as the cases, which coincide with a rainy season, usually peak in March and dwindle in subsequent months, but they have not this year.

"As of June...we can still see 100 to 500 cases of dengue fever a day," Tarmizi said at a press conference in Jakarta. "We don't know why there has been something different this year."

Further complicating the matter is the new coronavirus pandemic. Of the 460 jurisdictions in the country's 34 provinces reporting cases of dengue fever, 439 of them have also reported cases of COVID-19, the respiratory disease caused by the virus.

In some cases, people have developed both dengue fever and COVID-19, she said.

"It is possible that those getting infected with COVID-19 have a risk of getting infected with dengue fever," Tarmizi said, warning that like the coronavirus disease, there is no medicine to treat dengue fever and an available vaccine "doesn't work effectively."

Cases of dengue fever nationwide have declined every year since 2016 when 204,171 people were infected. In Indonesia, the disease claimed 1,598 lives in 2016, 493 in 2017, 344 in 2018 and 917 in 2019.

Mosquitoes carrying the dengue virus appear in Indonesia more frequently when the country transitions from the rainy season to the dry season between March and April.

Dengue fever causes flu-like symptom and occasionally develops into potentially lethal severe dengue.

Related coverage:

Masks for nightclub hostesses developed by Japan kimono maker

Japan's pro baseball, football leagues to admit fans from July 10

Japan fireworks makers look to light up coronavirus-hit industry