Arboviral Etiologies of Acute Febrile Illnesses in Western South America, 2000–2007

Abstract

BackgroundArthropod-borne viruses (arboviruses) are among the most common agents of human febrile illness worldwide and the most important emerging pathogens, causing multiple notable epidemics of human disease over recent decades. Despite the public health relevance, little is know about the geographic distribution, relative impact, and risk factors for arbovirus infection in many regions of the world. Our objectives were to describe the arboviruses associated with acute undifferentiated febrile illness in participating clinics in four countries in South America and to provide detailed epidemiological analysis of arbovirus infection in Iquitos, Peru, where more extensive monitoring was conducted.Methodology/FindingsA clinic-based syndromic surveillance system was implemented in 13 locations in Ecuador, Peru, Bolivia, and Paraguay. Serum samples and demographic information were collected from febrile participants reporting to local health clinics or hospitals. Acute-phase sera were tested for viral infection by immunofluorescence assay or RT-PCR, while acute- and convalescent-phase sera were tested for pathogen-specific IgM by ELISA. Between May 2000 and December 2007, 20,880 participants were included in the study, with evidence for recent arbovirus infection detected for 6,793 (32.5%). Dengue viruses (Flavivirus) were the most common arbovirus infections, totaling 26.0% of febrile episodes, with DENV-3 as the most common serotype. Alphavirus (Venezuelan equine encephalitis virus [VEEV] and Mayaro virus [MAYV]) and Orthobunyavirus (Oropouche virus [OROV], Group C viruses, and Guaroa virus) infections were both observed in approximately 3% of febrile episodes. In Iquitos, risk factors for VEEV and MAYV infection included being male and reporting to a rural (vs urban) clinic. In contrast, OROV infection was similar between sexes and type of clinic.Conclusions/SignificanceOur data provide a better understanding of the geographic range of arboviruses in South America and highlight the diversity of pathogens in circulation. These arboviruses are currently significant causes of human illness in endemic regions but also have potential for further expansion. Our data provide a basis for analyzing changes in their ecology and epidemiology.

House-to-house human movement drives dengue virus transmission

“…We estimated 99% specificity and 85% sensitivity for detecting DENV-4 seroconversions by PRNT assay. Acute samples from febrile cases and cluster participants were tested by RT-PCR and inoculated onto C6/36 cells for virus isolation as described previously (50). Acute and convalescent samples from cluster participants were assayed for virus by RT-PCE and virus isolation.…”

Lineage II of Southeast Asian/American DENV-2 is Associated with a Severe Dengue Outbreak in the Peruvian Amazon

“…Passive surveillance was conducted as previously described. 40 Briefly, patients 5 years of age or older who sought medical care at a participating outpatient clinic or hospital with an undifferentiated febrile illness ( 38 C for 5 days or less) were offered enrollment in the study. A standard questionnaire was used to obtain demographic and clinical information, and acute and convalescent blood samples were collected.…”

“…Viral isolation was performed from acutephase serum using both mosquito (C6/36) and African green monkey kidney (Vero) cells as previously described. 40 Briefly, serum was first diluted 1:10 in Eagle's minimal essential medium (Quality Biological Inc., Gaithersburg, MD) supplemented with 2% heat-inactivated fetal bovine serum (FBS; Sigma Aldrich, St. Louis, MO), 200 U/mL penicillin, and 200 μg streptomycin (Sigma Aldrich, St. Louis, MO). For C6/ 36 cell inoculations, 0.1 mL diluted serum was inoculated into duplicate wells of a 24-well plate.…”

“…6 (NAMRU-6) in conjunction with the Ministry of Health of Peru has conducted surveillance for the etiologies of febrile illness in several regions of Peru. 40 In October of 2010, this surveillance network detected the circulation of DENV-2 in Iquitos, Loreto, Peru. This finding was noteworthy, because DENV-2 had not been detected in this region since 2002.…”

Calling in sick: impacts of fever on intra-urban human mobility

“…First, febrile participants were classified as either having an active dengue infection at the time of the SSI (DENVþ), or having a fever for presumably some other reason (DENV2). This determination was made by testing acute and convalescent blood samples for dengue-specific IgM antibodies by antibody-capture ELISA and by testing acute samples for dengue viruses by realtime polymerase chain reaction [26]. Second, we categorized study participants according to four demographic classifications that we presume account for a large portion of inter-individual variation in mobility.…”