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Venezuelan equine encephalitis virus (VEEV) has been responsible for hundreds of thousands of human and equine cases of severe disease in the Americas. A passive surveillance study was conducted in Peru, Bolivia and Ecuador to determine the arboviral etiology of febrile illness. Patients with suspected viral-associated, acute, undifferentiated febrile illness of <7 days duration were enrolled in the study and blood samples were obtained from each patient and assayed by virus isolation. Demographic and clinical information from each patient was also obtained at the time of voluntary enrollment. In 2005-2007, cases of Venezuelan equine encephalitis (VEE) were diagnosed for the first time in residents of Bolivia; the patients did not report traveling, suggesting endemic circulation of VEEV in Bolivia. In 2001 and 2003, VEE cases were also identified in Ecuador. Since 1993, VEEV has been continuously isolated from patients in Loreto, Peru, and more recently (2005), in Madre de Dios, Peru. We performed phylogenetic analyses with VEEV from Bolivia, Ecuador and Peru and compared their relationships to strains from other parts of South America. We found that VEEV subtype ID Panama/Peru genotype is the predominant one circulating in Peru. We also demonstrated that VEEV subtype ID strains circulating in Ecuador belong to the Colombia/Venezuela genotype and VEEV from Madre de Dios, Peru and Cochabamba, Bolivia belong to a new ID genotype. In summary, we identified a new major lineage of enzootic VEEV subtype ID, information that could aid in the understanding of the emergence and evolution of VEEV in South America.

Arthropod-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. A 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. Our 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.

In late January 1991, epidemic cholera appeared in Peru. Within 2 months, 7922 cases and 17 deaths occurred in Piura, a Peruvian city of 361,868. A hospital-based culture surveyshowed that 79%–86% of diarrhea cases were cholera. High vibriocidal antibody titers were detected in 34% of the asymptomatic population. A study of 50 case-patients and 100 matched controls demonstrated that cholera was associated with drinking unboiled water (odds ratio [OR], 3.9; 95% confidence interval [CI], 1.7–8.9), drinking beverages from street vendors (OR, 14.6; CI, 4.2–51.2), and eating food from street vendors (OR, 24.0; CI, 3.0–191). In a second study, patients were more likely than controls to consume beverages with ice (OR, 4.0; CI, 1.1–18.3). Ice was produced from municipal water. Municipal water samples revealed no or insufficient chlorination, and fecal coliform bacteria were detected in samples from 6 of 10 wells tested. With epidemic cholera spreading throughout Latin America, these findings emphasize the importance of safe municipal drinking water.

Epidemic cholera struck Peru in January 1991 and spread within a month to the Amazon headwaters. A case-control study was done in the Amazonian city of Iquitos, Peru. Cholera-like illness was associated with eating unwashed fruits and vegetables (odds ratio [OR] = 8.0; 95% confidence limits [CL] = 2.2, 28.9) and drinking untreated water (OR = 2.9; 95% CL = 1.3, 6.4). Consumption of a drink made from toronja, a citrus fruit, was protective against illness (OR = 0.4; 95% CL = 0.2, 0.7). Illness was inversely associated with the quantity of toronja drink consumed (P < .01). Produce has not previously been convincingly documented as a risk factor for cholera; this study underscores the importance of washing produce before eating it. Acidic juices, such as toronja drink (pH 4.1), inhibit vibrio growth and may make contaminated water safer. Wild citrus fruits such as toronja are abundant, cheap, and popular in the Amazon region. Promoting the consumption of toronja drink may be a useful cholera prevention strategy in this region.