Japan had been free of dengue fever since 1945, but that streak is now over. More than 60 Japanese have come down with the disease since the end of August. Dengue is a viral infection transmitted by types of mosquitoes normally found in tropical and subtropical climates. Symptoms include high fever, severe headache, muscle and joint pains, nausea, swollen glands and rash. Most patients recover, but there is the possibility of deadly complications; dengue is a leading cause of death among children in parts of Asia and Latin America.

There is no immunization or specific treatment for dengue fever. There is, however, hope. A recent article by Andrew Pollack in The New York Times reported that an experimental vaccine developed by Sanofi proved about 60 percent effective in a large clinical trial involving more than 20,000 children ages 9 to 16 in several countries in Latin America and the Caribbean.

The outbreak in Japan is yet another reminder of the dangerous consequences of global warming. At a recent conference in Geneva, the World Health Organization warned of increases in dengue fever and other climate-sensitive diseases in unexpected parts of the world.

Higher temperatures and humidity causes mosquitoes to live longer and enlarges the geographic areas where they can spread the disease. While only nine countries experienced severe dengue before 1970, the disease is now endemic in more than 100 countries. Malaria, another mosquito-borne infection, is also on the rise. Health authorities have closed and fumigated parks in Tokyo where infected mosquitoes were found.