Puerto Rico's health department has declared a dengue epidemic.
Health Secretary Lorenzo Gonzalez said Monday that at least six people have died, including two children younger than 10. A total of 4,816 cases have been reported, including 21 cases of the potentially fatal hemorrhagic dengue.
The U.S. Centers for Disease Control and Prevention says 342 new cases were reported in one week last month, twice the number of cases during the same period last year.
Dengue cases usually flare up from August to January.
The mosquito-borne virus causes fever, severe headaches and extreme joint and muscle pain. Dengue claimed a record 31 lives during a 2010 epidemic that saw more than 12,000 suspected cases.