Japanese health officials say that three young people have contracted dengue fever, the first such infections in the country in nearly 70 years.

The three are suspected of having contracted the disease, called denguetsu in Japanese, when they were bitten by mosquitos in Yoyogi Park in central Tokyo, officials say.

The patients, a man in his 20s in Tokyo as well as a teen and woman in her 20s in Saitama Prefecture north of the capital, go to the same educational institution in Tokyo. None of them is in a life-threatening condition, officials says.

While there have been cases of the fever in Japan, this is the first reported domestic infection since 1945. – Filepic

The last domestic infection of dengue fever was in 1945, although there are around 200 cases annually among those who have travelled abroad, mainly in Southeast Asia.

Dengue fever is not transmitted directly from person-to-person and symptoms range from mild fever, to incapacitating high temperatures, according to the World Health Organization.

There is no vaccine or any specific medicine to treat dengue and patients should rest, drink plenty of fluids and reduce the fever using paracetamol or see a doctor, it says. The disease is carried by the Aedes mosquito also called the tiger mosquito in Japan.

Japanese officials say they have not detected the dengue virus in mosquitoes caught in Yoyogi Park but they will disinfect areas where patients were bitten.

Yoyogi Park, which sits next to the grand Meiji Jingu Shrine and is one of central Tokyo's biggest public green spaces, is popular with Tokyoites and tourists alike. – AFP

How the infection works

Do you know enough about dengue fever? Here is a in-depth look at the mosquito and how the virus works once it enters the body.