An outbreak of primary dengue infection among migrant Chinese workers in Singapore characterized by prominent gastrointestinal symptoms and a high proportion of symptomatic cases.

BACKGROUND: An outbreak of dengue occurred among Chinese migrant workers at a construction site in Singapore that was characterized by a number of unusual features. METHODS: Clinical and laboratory data were prospectively collected from workers who were hospitalized with fever. We compared the frequency of disease manifestations in these patients with historical data from other cases of dengue admitted to the same centre. A serological survey was performed at the construction site one month after the onset of the outbreak. RESULTS: Thirty-nine patients were admitted from the affected construction site with confirmed acute dengue infection in March and April 2002. Fever, headache and rash were common and occurred at similar frequency in outbreak patients and historical controls. Gastrointestinal manifestations were significantly more common in the outbreak patients compared with controls (nausea 68%, diarrhea 41%, hyponatremia 47% and elevated urea 20%). Of the 274 studied in the serological survey, 27 had serological evidence of acute dengue, of whom 24 (89%) had experienced a febrile illness in the previous month. The virus was cultured and identified as Dengue-2. Few patients had a positive IgG for dengue indicating that this was likely a primary infection. CONCLUSION: This outbreak of primary dengue infection was characterized by unusually prominent gastrointestinal symptoms and a high proportion of symptomatic transmission. Manifestations of dengue may be altered when outbreaks involve immunologically naïve adults who have migrated to dengue endemic areas.