RESUMO
BACKGROUND: Accurate seroprevalence estimates of SARS-CoV-2 in different populations could clarify the extent to which current testing strategies are identifying all active infection, and hence the true magnitude and spread of the infection. Our primary objective was to identify valid seroprevalence studies of SARS-CoV-2 infection and compare their estimates with the reported, and imputed, COVID-19 case rates within the same population at the same time point. METHODS: We searched PubMed, Embase, the Cochrane COVID-19 trials, and Europe-PMC for published studies and pre-prints that reported anti-SARS-CoV-2 IgG, IgM and/or IgA antibodies for serosurveys of the general community from 1 Jan to 12 Aug 2020. RESULTS: Of the 2199 studies identified, 170 were assessed for full text and 17 studies representing 15 regions and 118,297 subjects were includable. The seroprevalence proportions in 8 studies ranged between 1%-10%, with 5 studies under 1%, and 4 over 10%-from the notably hard-hit regions of Gangelt, Germany; Northwest Iran; Buenos Aires, Argentina; and Stockholm, Sweden. For seropositive cases who were not previously identified as COVID-19 cases, the majority had prior COVID-like symptoms. The estimated seroprevalences ranged from 0.56-717 times greater than the number of reported cumulative cases-half of the studies reported greater than 10 times more SARS-CoV-2 infections than the cumulative number of cases. CONCLUSIONS: The findings show SARS-CoV-2 seroprevalence is well below "herd immunity" in all countries studied. The estimated number of infections, however, were much greater than the number of reported cases and deaths in almost all locations. The majority of seropositive people reported prior COVID-like symptoms, suggesting that undertesting of symptomatic people may be causing a substantial under-ascertainment of SARS-CoV-2 infections.
Assuntos
Anticorpos Antivirais/sangue , COVID-19 , Isotipos de Imunoglobulinas/sangue , Adolescente , Adulto , Idoso , Argentina , COVID-19/epidemiologia , COVID-19/imunologia , Feminino , Alemanha , Humanos , Imunidade Coletiva , Incidência , Irã (Geográfico) , Masculino , Pessoa de Meia-Idade , Estudos Soroepidemiológicos , Suécia , Adulto JovemRESUMO
Viruses transmitted by Aedes mosquitoes, such as dengue, Zika, and chikungunya, have expanding ranges and seem unabated by current vector control programs. Effective control of these pathogens likely requires integrated approaches. We evaluated dengue management options in an endemic setting that combine novel vector control and vaccination using an agent-based model for Yucatán, Mexico, fit to 37 y of data. Our intervention models are informed by targeted indoor residual spraying (TIRS) experiments; trial outcomes and World Health Organization (WHO) testing guidance for the only licensed dengue vaccine, CYD-TDV; and preliminary results for in-development vaccines. We evaluated several implementation options, including varying coverage levels; staggered introductions; and a one-time, large-scale vaccination campaign. We found that CYD-TDV and TIRS interfere: while the combination outperforms either alone, performance is lower than estimated from their separate benefits. The conventional model hypothesized for in-development vaccines, however, performs synergistically with TIRS, amplifying effectiveness well beyond their independent impacts. If the preliminary performance by either of the in-development vaccines is upheld, a one-time, large-scale campaign followed by routine vaccination alongside aggressive new vector control could enable short-term elimination, with nearly all cases avoided for a decade despite continuous dengue reintroductions. If elimination is impracticable due to resource limitations, less ambitious implementations of this combination still produce amplified, longer-lasting effectiveness over single-approach interventions.
Assuntos
Vacinas contra Dengue , Dengue/prevenção & controle , Programas de Imunização , Modelos Biológicos , Controle de Mosquitos/métodos , Animais , Dengue/epidemiologia , Vacinas contra Dengue/administração & dosagem , Vacinas contra Dengue/imunologia , Vacinas contra Dengue/uso terapêutico , Vírus da Dengue/imunologia , Humanos , México , Mosquitos VetoresRESUMO
The understanding of immunological interactions among the four dengue virus (DENV) serotypes and their epidemiological implications is often hampered by the lack of individual-level infection history. Using a statistical framework that infers full infection history, we analyze a prospective pediatric cohort in Nicaragua to characterize how infection history modulates the risks of DENV infection and subsequent clinical disease. After controlling for age, one prior infection is associated with 54% lower, while two or more are associated with 91% higher, risk of a new infection, compared to DENV-naive children. Children >8 years old have 55% and 120% higher risks of infection and subsequent disease, respectively, than their younger peers. Among children with ≥1 prior infection, intermediate antibody titers increase, whereas high titers lower, the risk of subsequent infection, compared with undetectable titers. Such complex dependency needs to be considered in the design of dengue vaccines and vaccination strategies.
Assuntos
Anticorpos Antivirais/sangue , Vírus da Dengue/patogenicidade , Dengue/imunologia , Interações entre Hospedeiro e Microrganismos/imunologia , Vacinação/métodos , Adolescente , Fatores Etários , Anticorpos Antivirais/imunologia , Criança , Pré-Escolar , Reações Cruzadas/genética , Reações Cruzadas/imunologia , Dengue/sangue , Dengue/epidemiologia , Dengue/virologia , Vírus da Dengue/genética , Vírus da Dengue/imunologia , Vírus da Dengue/isolamento & purificação , Feminino , Humanos , Masculino , Nicarágua/epidemiologia , Estudos Prospectivos , Fatores de Risco , Sorogrupo , Virulência/genética , Virulência/imunologiaRESUMO
According to the World Health Organization, 98% of fatal dengue cases can be prevented; however, endemic countries such as Colombia have recorded higher case fatality rates during recent epidemics. We aimed to identify the predictors of mortality that allow risk stratification and timely intervention in patients with dengue. We conducted a hospital-based, case-control (1:2) study in two endemic areas of Colombia (2009-2015). Fatal cases were defined as having either 1) positive serological test (IgM or NS1), 2) positive virological test (RT-PCR or viral isolation), or 3) autopsy findings compatible with death from dengue. Controls (matched by state and year) were hospitalized nonfatal patients and had a positive serological or virological dengue test. Exposure data were extracted from medical records by trained staff. We used conditional logistic regression (adjusting for age, gender, disease's duration, and health-care provider) in the context of multiple imputation to estimate exposure to case-control associations. We evaluated 110 cases and 217 controls (mean age: 35.0 versus 18.9; disease's duration pre-admission: 4.9 versus 5.0 days). In multivariable analysis, retro-ocular pain (odds ratios [OR] = 0.23), nausea (OR = 0.29), and diarrhea (OR = 0.19) were less prevalent among fatal than nonfatal cases, whereas increased age (OR = 2.46 per 10 years), respiratory distress (OR = 16.3), impaired consciousness (OR = 15.9), jaundice (OR = 32.2), and increased heart rate (OR = 2.01 per 10 beats per minute) increased the likelihood of death (AUC: 0.97, 95% confidence interval: 0.96, 0.99). These results provide evidence that features of severe dengue are associated with higher mortality, which strengthens the recommendations related to triaging patients in dengue-endemic areas.
Assuntos
Diarreia/diagnóstico , Icterícia/diagnóstico , Náusea/diagnóstico , Síndrome do Desconforto Respiratório/diagnóstico , Dengue Grave/diagnóstico , Taquicardia/diagnóstico , Adolescente , Adulto , Anticorpos Antivirais/sangue , Estudos de Casos e Controles , Colômbia , Vírus da Dengue/imunologia , Vírus da Dengue/isolamento & purificação , Diarreia/mortalidade , Diarreia/fisiopatologia , Diarreia/virologia , Doenças Endêmicas , Feminino , Cefaleia , Humanos , Imunoglobulina M/sangue , Icterícia/mortalidade , Icterícia/fisiopatologia , Icterícia/virologia , Modelos Logísticos , Masculino , Pessoa de Meia-Idade , Náusea/mortalidade , Náusea/fisiopatologia , Náusea/virologia , Síndrome do Desconforto Respiratório/mortalidade , Síndrome do Desconforto Respiratório/fisiopatologia , Síndrome do Desconforto Respiratório/virologia , Medição de Risco , Dengue Grave/mortalidade , Dengue Grave/fisiopatologia , Dengue Grave/virologia , Análise de Sobrevida , Taquicardia/mortalidade , Taquicardia/fisiopatologia , Taquicardia/virologiaRESUMO
Dengue is the most prevalent mosquito-borne viral disease of humans and is caused by the four serotypes of dengue virus. To estimate the incidence of dengue and other arboviruses, we analyzed the baseline and first year follow-up of a prospective school-based cohort study and their families in three cities in the state of Yucatan, Mexico. Through enhanced surveillance activities, acute febrile illnesses in the participants were detected and yearly blood samples were collected to evaluate dengue infection incidence. A Cox model was fitted to identify hazard ratios of arboviral infections in the first year of follow-up of the cohort. The incidence of dengue symptomatic infections observed during the first year of follow-up (2015-2016) was 3.5 cases per 1,000 person-years (95% CI: 1.9, 5.9). The incidence of dengue infections was 33.9 infections per 1,000 person-years (95% CI: 31.7, 48.0). The majority of dengue infections and seroconversions were observed in the younger age groups (≤ 14 years old). Other arboviruses were circulating in the state of Yucatan during the study period. The incidence of symptomatic chikungunya infections was 8.6 per 1,000 person-years (95% CI: 5.8, 12.3) and the incidence of symptomatic Zika infections was 2.3 per 1,000 person-years (95% CI: 0.9, 4.5). Our model shows that having a dengue infection during the first year of follow-up was significantly associated with being female, living in Ticul or Progreso, and being dengue naïve at baseline. Age was not significantly associated with the outcome, it was confounded by prior immunity to dengue that increases with age. This is the first report of a cohort in Latin America that provides incidence estimates of the three arboviruses co-circulating in all age groups. This study provides important information for understanding the epidemiology of dengue and other arboviruses and better informing public health policies.
Assuntos
Infecções por Arbovirus/epidemiologia , Dengue/epidemiologia , Adolescente , Adulto , Infecções por Arbovirus/virologia , Arbovírus/fisiologia , Criança , Pré-Escolar , Estudos de Coortes , Dengue/virologia , Vírus da Dengue/fisiologia , Família , Feminino , Seguimentos , Humanos , Masculino , México/epidemiologia , Pessoa de Meia-Idade , Prevalência , Estudantes/estatística & dados numéricos , Adulto JovemRESUMO
BACKGROUND: The implementation of vector control interventions and potential introduction new tools requires baseline data to evaluate their direct and indirect effects. The objective of the study is to present the seroprevalence of dengue infection in a cohort of children 0 to 15 years old followed during 2015 to 2016, the risk factors and the role of enhanced surveillance strategies in three urban sites (Merida, Ticul and Progreso) in Yucatan, Mexico. METHODS: A cohort of school children and their family members was randomly selected in three urban areas with different demographic, social conditions and levels of transmission. We included results from 1,844 children aged 0 to 15 years. Serum samples were tested for IgG, NS1 and IgM. Enhanced surveillance strategies were established in schools (absenteeism) and cohort families (toll-free number). RESULTS: Seroprevalence in children 0 to 15 years old was 46.8 (CI 95% 44.1-49.6) with no difference by sex except in Ticul. Prevalence increased with age and was significantly lower in 0 to 5 years old (26.9%, 95% CI:18.4-35.4) compared with 6 to 8 years old (43.9%, 95% CI:40.1-47.7) and 9 to 15 years old (61.4%, 95% CI:58.0-64.8). Sharing the domestic space with other families increased the risk 1.7 times over the individual families that own or rented their house, while risk was significantly higher when kitchen and bathroom were outside. Complete protection with screens in doors and windows decreased risk of infection. Seroprevalence was significantly higher in the medium and high risk areas. CONCLUSIONS: The prevalence of antibodies in children 0 to 15 years in three urban settings in the state of Yucatan describe the high exposure and the heterogenous transmission of dengue virus by risk areas and between schools in the study sites. The enhanced surveillance strategy was useful to improve detection of dengue cases with the coincident transmission of chikungunya and Zika viruses.
Assuntos
Anticorpos Antivirais/sangue , Dengue/sangue , Adolescente , Criança , Pré-Escolar , Estudos de Coortes , Dengue/epidemiologia , Dengue/virologia , Vírus da Dengue/genética , Vírus da Dengue/imunologia , Vírus da Dengue/fisiologia , Feminino , Humanos , Lactente , Masculino , México/epidemiologia , Estudos Soroepidemiológicos , Irmãos , Estudantes/estatística & dados numéricosRESUMO
We use a data-driven global stochastic epidemic model to analyze the spread of the Zika virus (ZIKV) in the Americas. The model has high spatial and temporal resolution and integrates real-world demographic, human mobility, socioeconomic, temperature, and vector density data. We estimate that the first introduction of ZIKV to Brazil likely occurred between August 2013 and April 2014 (90% credible interval). We provide simulated epidemic profiles of incident ZIKV infections for several countries in the Americas through February 2017. The ZIKV epidemic is characterized by slow growth and high spatial and seasonal heterogeneity, attributable to the dynamics of the mosquito vector and to the characteristics and mobility of the human populations. We project the expected timing and number of pregnancies infected with ZIKV during the first trimester and provide estimates of microcephaly cases assuming different levels of risk as reported in empirical retrospective studies. Our approach represents a modeling effort aimed at understanding the potential magnitude and timing of the ZIKV epidemic and it can be potentially used as a template for the analysis of future mosquito-borne epidemics.
Assuntos
Infecção por Zika virus/epidemiologia , Aedes/virologia , América/epidemiologia , Animais , Brasil/epidemiologia , Epidemias , Feminino , Humanos , Recém-Nascido , Masculino , Microcefalia/complicações , Microcefalia/epidemiologia , Modelos Biológicos , Modelos Estatísticos , Mosquitos Vetores/virologia , Gravidez , Complicações Infecciosas na Gravidez/epidemiologia , Estudos Retrospectivos , Fatores de Risco , Processos Estocásticos , Zika virus/isolamento & purificação , Infecção por Zika virus/transmissãoRESUMO
Transmission of Zika virus (ZIKV) was first detected in Colombia in September 2015. As of April 2016, Colombia had reported over 65,000 cases of Zika virus disease (ZVD). We analysed daily surveillance data of ZVD cases reported to the health authorities of San Andres and Girardot, Colombia, between September 2015 and January 2016. ZVD was laboratory-confirmed by reverse transcription-polymerase chain reaction (RT-PCR) in the serum of acute cases within five days of symptom onset. We use daily incidence data to estimate the basic reproductive number (R0) in each population. We identified 928 and 1,936 reported ZVD cases from San Andres and Girardot, respectively. The overall attack rate for reported ZVD was 12.13 cases per 1,000 residents of San Andres and 18.43 cases per 1,000 residents of Girardot. Attack rates were significantly higher in females in both municipalities (p < 0.001). Cases occurred in all age groups with highest rates in 20 to 49 year-olds. The estimated R0 for the Zika outbreak was 1.41 (95% confidence interval (CI): 1.15-1.74) in San Andres and 4.61 (95% CI: 4.11-5.16) in Girardot. Transmission of ZIKV is ongoing in the Americas. The estimated R0 from Colombia supports the observed rapid spread.
Assuntos
Número Básico de Reprodução , Surtos de Doenças , Vigilância da População , Infecção por Zika virus/epidemiologia , Infecção por Zika virus/transmissão , Zika virus/isolamento & purificação , Adolescente , Adulto , Distribuição por Idade , Idoso , Criança , Pré-Escolar , Colômbia/epidemiologia , Estudos Epidemiológicos , Feminino , Humanos , Incidência , Lactente , Recém-Nascido , Masculino , Pessoa de Meia-Idade , Reação em Cadeia da Polimerase em Tempo Real , Distribuição por Sexo , Adulto Jovem , Zika virus/genéticaRESUMO
Dengue vaccines will soon provide a new tool for reducing dengue disease, but the effectiveness of widespread vaccination campaigns has not yet been determined. We developed an agent-based dengue model representing movement of and transmission dynamics among people and mosquitoes in Yucatán, Mexico, and simulated various vaccine scenarios to evaluate effectiveness under those conditions. This model includes detailed spatial representation of the Yucatán population, including the location and movement of 1.8 million people between 375,000 households and 100,000 workplaces and schools. Where possible, we designed the model to use data sources with international coverage, to simplify re-parameterization for other regions. The simulation and analysis integrate 35 years of mild and severe case data (including dengue serotype when available), results of a seroprevalence survey, satellite imagery, and climatological, census, and economic data. To fit model parameters that are not directly informed by available data, such as disease reporting rates and dengue transmission parameters, we developed a parameter estimation toolkit called AbcSmc, which we have made publicly available. After fitting the simulation model to dengue case data, we forecasted transmission and assessed the relative effectiveness of several vaccination strategies over a 20 year period. Vaccine efficacy is based on phase III trial results for the Sanofi-Pasteur vaccine, Dengvaxia. We consider routine vaccination of 2, 9, or 16 year-olds, with and without a one-time catch-up campaign to age 30. Because the durability of Dengvaxia is not yet established, we consider hypothetical vaccines that confer either durable or waning immunity, and we evaluate the use of booster doses to counter waning. We find that plausible vaccination scenarios with a durable vaccine reduce annual dengue incidence by as much as 80% within five years. However, if vaccine efficacy wanes after administration, we find that there can be years with larger epidemics than would occur without any vaccination, and that vaccine booster doses are necessary to prevent this outcome.
Assuntos
Vacinas contra Dengue , Dengue/epidemiologia , Dengue/prevenção & controle , Adolescente , Criança , Pré-Escolar , Simulação por Computador , Dengue/economia , Dengue/transmissão , Vacinas contra Dengue/administração & dosagem , Vacinas contra Dengue/economia , Vacinas contra Dengue/imunologia , Epidemias/prevenção & controle , Feminino , Previsões , Humanos , Programas de Imunização , Imunização Secundária , Incidência , Masculino , México/epidemiologia , Estudos Soroepidemiológicos , Vacinação/tendênciasRESUMO
A systematic literature review was conducted to describe the epidemiology of dengue disease in Colombia. Searches of published literature in epidemiological studies of dengue disease encompassing the terms "dengue", "epidemiology," and "Colombia" were conducted. Studies in English or Spanish published between 1 January 2000 and 23 February 2012 were included. The searches identified 225 relevant citations, 30 of which fulfilled the inclusion criteria defined in the review protocol. The epidemiology of dengue disease in Colombia was characterized by a stable "baseline" annual number of dengue fever cases, with major outbreaks in 2001-2003 and 2010. The geographical spread of dengue disease cases showed a steady increase, with most of the country affected by the 2010 outbreak. The majority of dengue disease recorded during the review period was among those <15 years of age. Gaps identified in epidemiological knowledge regarding dengue disease in Colombia may provide several avenues for future research, namely studies of asymptomatic dengue virus infection, primary versus secondary infections, and under-reporting of the disease. Improved understanding of the factors that determine disease expression and enable improvement in disease control and management is also important.