A second dengue infection can turn the milder virus deadly
Most dengue cases barely register, yet a later bout with a different serotype raises the odds of severe disease through antibody-dependent enhancement. Four confirmed types circulate via Aedes mosquitoes—especially Aedes aegypti—across more than a hundred countries and into warming temperate edges.
Symptoms typically appear three to fourteen days after a bite, often clustering around days four to seven: high fever, headache, vomiting, muscle and joint pain, itching, and rash. Recovery for uncomplicated illness usually takes two to seven days. About eighty percent of infections stay mild or silent; roughly five percent become more severe, and a smaller share threaten life with bleeding, shock, or organ stress. Clinicians divide the course into febrile, critical, and recovery phases, watching the dangerous window after peak fever most carefully for warning signs.
Infection with one serotype usually confers lifelong protection against that type only, with brief cross-protection that fades. Vaccines arrived late relative to the burden: Dengvaxia in 2016, recommended mainly to prevent reinfection in people already exposed, and Qdenga in 2022 for broader age groups from four years upward. Prevention still leans on destroying mosquito breeding water and avoiding bites. Outbreak descriptions stretch back to 1779; viral transmission was understood by the early twentieth century, yet the disease remains classified among neglected tropical infections.
By 2023 more than five million cases were counted worldwide as dengue pushed from classic tropics toward Iberia and southern U.S. states, a shift partly linked to climate. The clinical puzzle is immunological: antibodies that mark past exposure can, in the wrong sequel, help a new serotype invade more aggressively. That twist turns a usually self-limiting fever into a public-health moving target.
Source: Dengue fever
