The swine flu outbreak in Mexico during the weekend made majority of the foreign exchange market players go for purchasing of more safe currencies. The most popular in this range is the Japanese Yen, most likely because the country is isolated from the disease geographically.
As Japan is an island, it will be much easier for the country to keep the swine flu away from its coasts, and as for now, there are no signs or cases of swine flu in the country.