The health ministry said Friday it is stepping up surveillance of the Zika virus and from Feb. 15 will require doctors to report infections to public health centers.
Designation of diseases in this way is usually the result of consideration by a specialist panel with input from the public, but officials fast-tracked the process after the World Health Organization declared the mosquito-borne virus an international emergency on Monday.
Infections are spreading rapidly in Latin America.
The decision also provides for people entering Japan to be screened for the virus at quarantine stations from Feb. 15.
The ministry plans to distribute Zika virus testing kits to regional public health institutes and quarantine stations nationwide by early next month.
Health, Labor and Welfare Minister Yasuhisa Shiozaki said Friday much uncertainty remains about the nature of the virus following U.S. reports it can be transmitted sexually.
"We will continue to gather information and take every necessary measure," Shiozaki said.