Dengue is a viral infection that’s common in countries with subtropical and tropical climates. It is transmitted through the bite of a female mosquito (Aedes aegypti or A. albopictus) carrying the dengue virus (DENV). Although many cases of DENV infection involve only mild symptoms, severe dengue can be life-threatening and requires hospitalization. According to the World Health Organization (WHO), there are four distinct, but closely related, serotypes of DENV. This means that a person can be infected by the virus as many as four times. Studies have also found that people who recover from infection by one serotype only develop partial and temporary cross-immunity to the other serotypes. Subsequent infections by other serotypes increases a person’s risk of developing severe dengue.