Sika is a virus, the virus with the Aedes genus, so the contact comes from mosquitoes who bite. You may also contact via blood or spreading out of maternal sick fetus.
Sika is a viral infection of the mosquito-borne virus. The contact came from an infected mosquito bite. You may also contact them by blood. Or spread from a sick mother to the fetus.
The virus is a virus that cigarette mosquito as carrier. So contact was from mosquito with infections, Ltd. It may also contact the blood. Or spread from mothers to the fetus.