Primary Dengue and Long-Term Health Status in Madeira Island, Portugal: A Retrospective Questionnaire-Based Study.

Dengue is among the most important mosquito-borne viral diseases worldwide. Although its acute manifestations are well known, little is known about the long-term impact of dengue on the population's health status. Madeira Island experienced a single outbreak of autochthonous dengue from September 2012 to March 2013. To extend our knowledge about the clinical impact of the outbreak on this naive population, we applied an online questionnaire to 168 adults diagnosed with dengue at the time to characterize retrospectively their symptoms during the infection and to identify long-term manifestations, possibly triggered by dengue. The most frequent symptoms during the clinical period, reported by more than three-quarters of our participants, were fever, myalgia, extreme tiredness, and headaches, whereas vomiting, pruritus, nausea, retro-orbital pain, and arthralgia occurred in 35% to 50% of participants. In the 8 years after dengue, 61.5% of participants reported at least one recurrent previously nonexistent symptom, the most frequent being headaches, abundant hair loss, extreme tiredness, arthralgia, and myalgia, experienced by 25% to 35% of participants. Nearly 20% of the participants with persistent symptoms reported the onset of chronic illness in the 4 years after dengue, most frequently ophthalmological and autoimmune diseases (5.6% each), versus only 2.2% of chronic disease onset in participants without persistent symptoms. Our results suggest that the occurrence of persistent symptoms after primary dengue might be more frequent than anticipated and may persist for several years, having an impact on the health status and well-being of a considerable proportion of the infected population.