Japan has confirmed 22 of its citizens have dengue fever.

The country hasn't had a dengue outbreak in almost 70 years. The last recorded outbreak was in 1945.

Dengue fever is a tropical disease carried and spread by mosquitoes. Its symptoms include very high fever, rashes, joint pain, muscle aches and headaches.

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Those suffering from a severe case of the disease are required to be treated in hospitals. Left untreated, dengue fever can be fatal.

Warnings about mosquitoes have been placed at Yoyogi Park in central Tokyo where officials believe the people infected with the virus have been bitten. Certain areas of the park have also been cordoned off from the public.

Workers in white overalls and masks as they spray insecticide in the park and drain ornamental ponds of water.

In recent years, Japan has had imported cases of dengue fever. But these cases mostly involve foreign tourists who catch the disease while travelling to other tropical areas.

Dengue is common in areas across Asia, Africa and Latin America.

Japanese officials believe local mosquitoes could have possibly bitten tourists infected with the virus and, consequently passed it on to others.