Study subjects included patients 5 years of age or older who presented in outpatient clinics or hospitals with acute, undifferentiated, febrile illness (greater than or equal to 38°C for 7 days duration or less) along with one or more of the following symptoms: headache, muscle, ocular and/or joint pain, generalized fatigue, cough, nausea, vomiting, sore throat, rhinorrhea, difficulty breathing, diarrhea, jaundice, dizziness, disorientation, stiff neck, or bleeding manifestations. Children younger than five years of age were included if they presented with hemorrhagic manifestations indicative of dengue hemorrhagic fever (DHF), including epistaxis, pleural effusion, platelets less than 100,000/ml, petechiae, or bloody stool or vomit. Exclusion criteria included fever in excess of seven days or an identifiable focus of infection, such as sinusitis, pneumonia, acute otitis media, or acute urinary tract infection. Demographic data, medical history, and clinical features for each patient were obtained using a standard questionnaire. In malaria-endemic regions if malaria was suspected, capillary blood from febrile patients was screened for Plasmodium spp. by clinic or hospital personnel according to routine diagnostic procedures at each site. Peripheral blood samples were screened by microscopic analysis of stained thick smear slides. In some sites, owing to the possibility of arbovirus co-infection, malaria-positive patients were subsequently invited to participate in the NMRCD study, with malaria results recorded along with symptoms and demographic information.
During the acute phase of illness blood samples were obtained from each patient, and when possible, convalescent samples were obtained 10 days to 4 weeks later for serological studies. For patients older than 10 years of age, up to 15 mL of blood was collected, and for patients younger than 10 years of age, up to 7 mL of blood was collected. Trained phlebotomists collected blood samples via arm venipuncture using standard methods and universal precautions.
During the acute phase of illness blood samples were obtained from each patient, and when possible, convalescent samples were obtained 10 days to 4 weeks later for serological studies. For patients older than 10 years of age, up to 15 mL of blood was collected, and for patients younger than 10 years of age, up to 7 mL of blood was collected. Trained phlebotomists collected blood samples via arm venipuncture using standard methods and universal precautions.
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