Epidemiology of Dengue Virus in Iquitos, Peru 1999 to 2005: Interepidemic and Epidemic Patterns of Transmission

To develop prevention (including vaccines) and control programs for dengue fever, a significant mosquito-borne disease in the tropics, there is an urgent need for comprehensive long term field epidemiological studies. We report results from a study that monitored ∼2,400 school children and some adult family members for dengue infection at 6 month intervals from 1999 to 2005, in the Amazonian city of Iquitos, Peru. At enrollment, ∼80% of the participants had a previous infection with DENV serotypes 1 and 2 or both. During the first 15 months, about 3 new infections for every 100 participants were observed among the study participants. In 2001, DENV-3, a serotype not previously observed in the region, invaded Iquitos in a process characterized by 3 distinct periods: amplification over at least a 5–6 month period, replacement of previously circulating serotypes, and epidemic transmission when incidence peaked. Incidence patterns of new infections were geographically distinct from baseline prevalence rates prior to arrival of DENV-3, but closely mirrored them during the invasion. DENV transmission varied geographically corresponding to elevated mosquito densities. The invasion of a novel serotype is often characterized by 5–6 months of silent transmission before traditional surveillance programs detect the virus. This article sets the stage for subsequent publications on dengue epidemiology

Multicountry Prospective Clinical Evaluation of Two Enzyme-Linked Immunosorbent Assays and Two Rapid Diagnostic Tests for Diagnosing Dengue Fever

We evaluated four dengue diagnostic devices from Alere, including the SD Bioline Dengue Duo (nonstructural [NS] 1 Ag and IgG/IgM), the Panbio Dengue Duo Cassette (IgM/IgG) rapid diagnostic tests (RDTs), and the Panbio dengue IgM and IgG capture enzyme-linked immunosorbent assays (ELISAs) in a prospective, controlled, multicenter study in Peru, Venezuela, Cambodia, and the United States, using samples from 1,021 febrile individuals. Archived, well-characterized samples from an additional 135 febrile individuals from Thailand were also used. Reference testing was performed on all samples using an algorithm involving virus isolation, in-house IgM and IgG capture ELISAs, and plaque reduction neutralization tests (PRNT) to determine the infection status of the individual. The primary endpoints were the clinical sensitivities and specificities of these devices. The SD Bioline Dengue Duo had an overall sensitivity of 87.3% (95% confidence interval [CI], 84.1 to 90.2%) and specificity of 86.8% (95% CI, 83.9 to 89.3%) during the first 14 days post-symptom onset (p.s.o.). The Panbio Dengue Duo Cassette demonstrated a sensitivity of 92.1% (87.8 to 95.2%) and specificity of 62.2% (54.5 to 69.5%) during days 4 to 14 p.s.o. The Panbio IgM capture ELISA had a sensitivity of 87.6% (82.7 to 91.4%) and specificity of 88.1% (82.2 to 92.6%) during days 4 to 14 p.s.o. Finally, the Panbio IgG capture ELISA had a sensitivity of 69.6% (62.1 to 76.4%) and a specificity of 88.4% (82.6 to 92.8%) during days 4 to 14 p.s.o. for identification of secondary dengue infections. This multicountry prospective study resulted in reliable real-world performance data that will facilitate data-driven laboratory test choices for managing patient care during dengue outbreaks

Circulating Strains of Human Respiratory Syncytial Virus in Central and South America

Human respiratory syncytial virus (HRSV) is a major cause of viral lower respiratory tract infections among infants and young children. HRSV strains vary genetically and antigenically and have been classified into two broad subgroups, A and B (HRSV-A and HRSV-B, respectively). To date, little is known about the circulating strains of HRSV in Latin America. We have evaluated the genetic diversity of 96 HRSV strains by sequencing a variable region of the G protein gene of isolates collected from 2007 to 2009 in Central and South America. Our results show the presence of the two antigenic subgroups of HRSV during this period with the majority belonging to the genotype HRSV-A2

Cambios dinámicos de citoquinas proinflamatorias, moléculas de adhesión y marcadores de activación linfocítica como indicadores tempranos de severidad en pacientes con Dengue

Varios mecanismos inmuno-patogénicos se han propuesto para explicar el incremento masivo de la permeabilidad vascularobservada en las formas severas de la infección por el Virus del Dengue (DENV). El objetivo del estudio fue determinar loscambios cinéticos de mediadores inflamatorios (IL-8, TNF-α), marcadores soluble de activación linfocítica temprana (sIL-2R,sTNF-Rp75) y fracciones solubles de moléculas de adhesión celular (sICAM-1, sVCAM-1) como marcadores tempranos deseveridad en pacientes con dengue. Veinte pacientes clasificados como Dengue (Dengue±Signos de Alarma,D±WS) y treintapacientes con Dengue Severo (DS) fueron incluidos en el estudio. Suero de individuos aparentemente saludables fueronincluidos como controles. En comparación con los individuos controles, los casos con Dengue mostraron niveles de IL-8 yTNF con diferencias no significativas en la fase febril o crítica de la enfermedad; sin embargo, un incremento significativo desICAM-1 y sVCAM-1 ocurrió en ambas fases, mientras que los niveles de sIL2R y sTNF-p75 se elevaron significativamentesolo en la fase crítica de la enfermedad. En comparación con los casos con dengue y controles, los pacientes con DS mostraron diferencias significativas en los niveles de IL-8 y TNF-α durante la fase crítica y un incremento significativo demoléculas de adhesión en ambas fases, pero los niveles más elevados de sVCAM-1 y sIL-2R fueron observados en la fasefebril. En conclusión, sIL-2R y sVCAM-1, como marcadores tempranos de activación linfocítica y endotelial, servirían comoindicadores de severidad en la fase aguda de la infección por el virus del dengue.Dinamic changes of pro-inflammatory cytokines, adhesion molecules and lymphocytesactivation markers as early indicators of diseases severity in patients with DengueAbstractSeveral immunopathogenic mechanisms have been proposed to explain the massive increase of vascular permeabilityobserved in the severe forms of infection by Dengue Virus (DENV). Our aim was to determine the kinetic changes ofinflammatory mediators (IL-8, TNF- α), soluble early lymphocyte activation markers (sIL-2R, sTNF-Rp75) and solublefractions of cell adhesion molecules (sICAM-1 and sVCAM-1) as indicators for early recognition of disease severity inpatients with laboratory-confirmed dengue. Twenty patients classified as Dengue±Warning Signs (D±WS) and thirty patientswith Severe Dengue (SD) were included in the study. Serums of apparently healthy individuals were included as controls.Compared with normal subjects, D±WS cases did not show significant differences in the levels of IL-8 or TNF-α during theacute nor in the critical stages of the disease; however, in D±WS cases levels of sICAM-1 and sVCAM-1 were higher thancontrols during both phases; in contrast, significant increase of sTNF-p75 and sIL2R levels were observed during the criticalphase of the disease. Compared with both dengue patients and controls, patients with SD showed significant rise in thelevels of IL-8 and TNF-α during the critical phase of the disease and a significant increase in adhesion molecules weredetected in both phases, but the highest levels of sVCAM-1 and sIL-2R were observed only during the acute stage of thedisease. In conclusion, sIL-2R and sVCAM-1, as early markers of lymphocyte and endothelial activation, would serves asindicators of severity during the acute phase of dengue infection

Molecular epidemiology of dengue virus type 3 in Venezuela.

During the past 40 years, dengue haemorrhagic fever and dengue shock syndrome (DHF/DSS) have emerged in humans, with approximately 3 million cases reported and over 58 000 deaths. Dengue virus serotypes 1, 2 and 4 (DENV-1, -2 and -4) have been co-circulating in Venezuela for at least the past 10 years, causing minor or major outbreaks of dengue fever (DF) and DHF/DSS. The first recorded outbreak due to DENV-3 in Venezuela dates to 1964 and the virus then seems to have disappeared. However, DENV-3 re-appeared recently (in July, 2000) in Venezuela after 32 years of absence and produced a prolonged major outbreak, which, by the end of 2001, involved 83 180 cases of dengue, mostly DF (92 %). Previous phylogenetic studies revealed that the DENV-3 circulating during the 1960s Latin American outbreak was a genotype V virus. To gain a better understanding of the nature of the current epidemic, the complete sequence was determined of the envelope (E) gene of 15 Venezuelan DENV-3 viruses isolated during 2000 and 2001 from patients presenting with different disease severity. Sequence data were used in phylogenetic comparisons with global samples of DENV-3. Analysis revealed that the strain circulating in Venezuela is closely related to isolates that were previously present in Panama and Nicaragua in 1994 and since then have spread through Central American countries and Mexico. This study also confirms previous reports showing that the DENV-3 strain currently circulating in the Americas is related to the strain that caused DHF epidemics in Sri Lanka and India in 1989-1991 (genotype III). Finally, no evidence of the re-emergence of the strain that circulated in Venezuela in the late 1960s and 1970s (genotype V) was found

Difference between the Abilities of Human Fcγ Receptor-Expressing CV-1 Cells To Neutralize American and Asian Genotypes of Dengue Virus 2▿

Sera from patients involved in a Peruvian outbreak of dengue virus serotype 1 infection cross-neutralized the American genotype of dengue virus serotype 2 up to 100-fold more efficiently than they did the virulent Asian genotype of dengue virus serotype 2, as determined by a plaque reduction neutralization test (PRNT) with CV-1 fibroblasts modified to express human Fcγ receptor CD32. The concordant preferential immune enhancement of the Asian genotype of dengue virus serotype 2 in human monocytes suggests that such a modification might strengthen the correlation between the PRNT titer and protection

Human Antibody Responses to Emerging Mayaro Virus and Cocirculating Alphavirus Infections Examined by Using Structural Proteins from Nine New and Old World Lineages

ABSTRACT Mayaro virus (MAYV), Venezuelan equine encephalitis virus (VEEV), and chikungunya virus (CHIKV) are vector-borne alphaviruses that cocirculate in South America. Human infections by these viruses are frequently underdiagnosed or misdiagnosed, especially in areas with high dengue virus endemicity. Disease may progress to debilitating arthralgia (MAYV, CHIKV), encephalitis (VEEV), and death. Few standardized serological assays exist for specific human alphavirus infection detection, and antigen cross-reactivity can be problematic. Therefore, serological platforms that aid in the specific detection of multiple alphavirus infections will greatly expand disease surveillance for these emerging infections. In this study, serum samples from South American patients with PCR- and/or isolation-confirmed infections caused by MAYV, VEEV, and CHIKV were examined by using a protein microarray assembled with recombinant capsid, envelope protein 1 (E1), and E2 from nine New and Old World alphaviruses. Notably, specific antibody recognition of E1 was observed only with MAYV infections, whereas E2 was specifically targeted by antibodies from all of the alphavirus infections investigated, with evidence of cross-reactivity to E2 of o’nyong-nyong virus only in CHIKV-infected patient serum samples. Our findings suggest that alphavirus structural protein microarrays can distinguish infections caused by MAYV, VEEV, and CHIKV and that this multiplexed serological platform could be useful for high-throughput disease surveillance. IMPORTANCE Mayaro, chikungunya, and Venezuelan equine encephalitis viruses are closely related alphaviruses that are spread by mosquitos, causing diseases that produce similar influenza-like symptoms or more severe illnesses. Moreover, alphavirus infection symptoms can be similar to those of dengue or Zika disease, leading to underreporting of cases and potential misdiagnoses. New methods that can be used to detect antibody responses to multiple alphaviruses within the same assay would greatly aid disease surveillance efforts. However, possible antibody cross-reactivity between viruses can reduce the quality of laboratory results. Our results demonstrate that antibody responses to multiple alphaviruses can be specifically quantified within the same assay by using selected recombinant protein antigens and further show that Mayaro virus infections result in unique responses to viral envelope proteins

A phylogenetic analysis using full-length viral genomes of South American dengue serotype 3 in consecutive Venezuelan outbreaks reveals a novel NS5 mutation

Dengue virus currently causes 50–100 million infections annually. Comprehensive knowledge about the evolution of Dengue in response to selection pressure is currently unavailable, but would greatly enhance vaccine design efforts. In the current study, we sequenced 187 new dengue virus serotype 3 (DENV-3) genotype III whole genomes isolated from Asia and the Americas. We analyzed them together with previously-sequenced isolates to gain a more detailed understanding of the evolutionary adaptations existing in this prevalent American serotype. In order to analyze the phylogenetic dynamics of DENV-3 during outbreak periods; we incorporated datasets of 48 and 11 sequences spanning two major outbreaks in Venezuela during 2001 and 2007–2008, respectively. Our phylogenetic analysis of newly sequenced viruses shows that subsets of genomes cluster primarily by geographic location, and secondarily by time of virus isolation. DENV-3 genotype III sequences from Asia are significantly divergent from those from the Americas due to their geographical separation and subsequent speciation. We measured amino acid variation for the E protein by calculating the Shannon entropy at each position between Asian and American genomes. We found a cluster of seven amino acid substitutions having high variability within E protein domain III, which has previously been implicated in serotype-specific neutralization escape mutants. No novel mutations were found in the E protein of sequences isolated during either Venezuelan outbreak. Shannon entropy analysis of the NS5 polymerase mature protein revealed that a G374E mutation, in a region that contributes to interferon resistance in other flaviviruses by interfering with JAK-STAT signaling was present in both the Asian and American sequences from the 2007–2008 Venezuelan outbreak, but was absent in the sequences from the 2001 Venezuelan outbreak. In addition to E, several NS5 amino acid changes were unique to the 2007–2008 epidemic in Venezuela and may give additional insight into the adaptive response of DENV-3 at the population level