The use of mosquito repellent containing DEET is recommended for travelers to the Punta Cana area, especially after two cases of malaria have been detected in US tourists returning from this tourist area. There have not been reports of malaria affecting tourists visiting other areas of the Dominican Republic. The Center for Disease Control of the United States has instated an alert to travelers to the area, and is recommending tourists take preventive measures. Around 1.3 million tourists traveled to Punta Cana last year.
For a report, see http://www.dr1.com/news/2004/120304_malaria.shtml