Andrea Olea

The influence of climatic conditions on the transmission dynamics of the 2009 A/H1N1 influenza pandemic in Chile

BackgroundThe role of demographic factors, climatic conditions, school cycles, and connectivity patterns in shaping the spatio-temporal dynamics of pandemic influenza is not clearly understood. Here we analyzed the spatial, age and temporal evolution of the 2009 A/H1N1 influenza pandemic in Chile, a southern hemisphere country covering a long and narrow strip comprising latitudes 17°S to 56°S.MethodsWe analyzed the dissemination patterns of the 2009 A/H1N1 pandemic across 15 regions of Chile based on daily hospitalizations for severe acute respiratory disease and laboratory confirmed A/H1N1 influenza infection from 01-May to 31-December, 2009. We explored the association between timing of pandemic onset and peak pandemic activity and several geographical and demographic indicators, school vacations, climatic factors, and international passengers. We also estimated the reproduction number (R) based on the growth rate of the exponential pandemic phase by date of symptoms onset, estimated using maximum likelihood methods.ResultsWhile earlier pandemic onset was associated with larger population size, there was no association with connectivity, demographic, school or climatic factors. In contrast, there was a latitudinal gradient in peak pandemic timing, representing a 16-39-day lag in disease activity from the southern regions relative to the northernmost region (P < 0.001). Geographical differences in latitude of Chilean regions, maximum temperature and specific humidity explained 68.5% of the variability in peak timing (P = 0.01). In addition, there was a decreasing gradient in reproduction number from south to north Chile (P < 0.0001). The regional mean R estimates were 1.6-2.0, 1.3-1.5, and 1.2-1.3 for southern, central and northern regions, respectively, which were not affected by the winter vacation period.ConclusionsThere was a lag in the period of most intense 2009 pandemic influenza activity following a South to North traveling pattern across regions of Chile, significantly associated with geographical differences in minimum temperature and specific humidity. The latitudinal gradient in timing of pandemic activity was accompanied by a gradient in reproduction number (P < 0.0001). Intensified surveillance strategies in colder and drier southern regions could lead to earlier detection of pandemic influenza viruses and improved control outcomes.

Dengue-1 Virus Isolation during First Dengue Fever Outbreak on Easter Island, Chile

Dengue virus was detected for the first time in Chile, in an outbreak of dengue fever on Easter Island. The virus was isolated in tissue culture and characterized by reverse transcription–polymerase chain reaction as being dengue type 1.

THE BASIC REPRODUCTION NUMBER R0 AND EFFECTIVENESS OF REACTIVE INTERVENTIONS DURING DENGUE EPIDEMICS: THE 2002 DENGUE OUTBREAK IN EASTER ISLAND, CHILE

We use a stochastic simulation model to explore the effect of reactive intervention strategies during the 2002 dengue outbreak in the small population of Easter Island, Chile. We quantified the effect of interventions on the transmission dynamics and epidemic size as a function of the simulated control intensity levels and the timing of initiation of control interventions. Because no dengue outbreaks had been reported prior to 2002 in Easter Island, the 2002 epidemic provided a unique opportunity to estimate the basic reproduction number R0 during the initial epidemic phase, prior to the start of control interventions. We estimated R0 at 27.2 (95%CI: 14.8, 49.3). We found that the final epidemic size is highly sensitive to the timing of start of interventions. However, even when the control interventions start several weeks after the epidemic onset, reactive intervention efforts can have a significant impact on the final epidemic size. Our results indicate that the rapid implementation of control interventions can have a significant effect in reducing the epidemic size of dengue epidemics.

Surveillance System for Infectious Diseases of Pets, Santiago, Chile

Pet diseases may pose risks to human health but are rarely included in surveillance systems. A pilot surveillance system of pet infectious diseases in Santiago, Chile, found that 4 canine and 3 feline diseases accounted for 90.1% and 98.4% of notifications, respectively. Data also suggested association between poverty and pet diseases.

Trends in mortality from respiratory disease in Latin America since 1998 and the impact of the 2009 influenza pandemic

OBJECTIVE To determine trends in mortality from respiratory disease in several areas of Latin America between 1998 and 2009. METHODS The numbers of deaths attributed to respiratory disease between 1998 and 2009 were extracted from mortality data from Argentina, southern Brazil, Chile, Costa Rica, Ecuador, Mexico and Paraguay. Robust linear models were then fitted to the rates of mortality from respiratory disease recorded between 2003 and 2009. FINDINGS Between 1998 and 2008, rates of mortality from respiratory disease gradually decreased in all age groups in most of the study areas. Among children younger than 5 years, for example, the annual rates of such mortality - across all seven study areas - fell from 56.9 deaths per 100,000 in 1998 to 26.6 deaths per 100,000 in 2008. Over this period, rates of mortality from respiratory disease were generally highest among adults older than 65 years and lowest among individuals aged 5 to 49 years. In 2009, mortality from respiratory disease was either similar to that recorded in 2008 or showed an increase - significant increases were seen among children younger than 5 years in Paraguay, among those aged 5 to 49 years in southern Brazil, Mexico and Paraguay and among adults aged 50 to 64 years in Mexico and Paraguay. CONCLUSION In much of Latin America, mortality from respiratory disease gradually fell between 1998 and 2008. However, this downward trend came to a halt in 2009, probably as a result of the (H1N1) 2009 pandemic.

Brote de gastroenteritis por Vibrio parahaemolyticus en Chile

El Vibrio parahaemolyticus cs una bacteria enterica, cuyo habitat natural son las costas marinas, pues requiere sal para su desarrollo. En Ia epoca de calor se cncuentra en las aguas litorales y mariscos bivalvos, mientras que en Ia epoca fria se encucntra en los sedimentos mannos. Se han notificado brotes en muchos paiscs del mundo, donde Ia fucntc inculpada han sido los mariscos crudos o mal cocidos ( ostras y almejas principalmente ). Los casos se presentan con mayor frecuencia en meses calidos. La transmisi6n se produce por Ia ingestion de mariscos, especialmente bivalvos, crudos o mal cocidos. Tambien se pucde dar por contaminaci6n cruzada de otros alimcntos (por Ia manipulaci6n incorrecta de mariscos crudos). La congelaci6n inapropiada de productos del mar contaminados favorece su proliferaci6n y Ia posibilidad de infectar. No se transmitc de persona a persona. El pcriodo de incubaci6n es de 12 a 24 hrs, lucgo del cual se produce un cuadro intestinal (enteritis) caracterizado por diarrea acuosa y c6licos abdominales, que puede acompaf1arse de nauseas, v6mitos, fiebre y cefalea. Generalmente es autolimitado y dura alredcdor de 3 dias (rango l a 7). La muerte por esta causa cs muy rara. En brotes ocuiTidos en Australia, Estados Unidos y Reino Unido, Ia letalidad no supera el 0,5%. La medida principal es Ia hidrataci6n para reponer los

Rubella Outbreaks Following Virus Importations: The Experience of Chile

BACKGROUND Strategies for accelerated control of rubella and congenital rubella syndrome (CRS) in Chile included mass vaccination of women of childbearing age in 1999 but did not include vaccination of adult men. METHODS We reviewed data from Chiles integrated surveillance system for measles, rubella, and CRS from 2004 through 2009 and describe the epidemiology of rubella outbreaks and implementation of control measures in 2005 and 2007 following mass vaccination of women. Population estimates from census data were used to calculate rubella incidence rates. The age distribution of rubella cases during 2007 was compared with rubella vaccination opportunities by birth cohort to orient mass vaccination of adult men. RESULTS In 2005, an institutional outbreak of rubella occurred among male naval recruits 18-22 years of age, with 46 confirmed cases over a 5-month period. Beginning in March 2007, rubella outbreaks among young adults in the capital of Santiago spread throughout Chile, resulting in >4000 confirmed rubella cases. Delayed control measures and rapid dissemination among young adults led to widespread transmission. From 2007 through 2009, rubella incidence was highest among adult men not included in previous vaccination strategies. Mass vaccination of men 19-29 years of age was conducted in November 2007 to interrupt rubella transmission. CONCLUSIONS Chiles experience suggests that vaccination strategies for rubella and CRS elimination need to include both men and women.

Vigilancia de brotes de enfermedades transmitidas por alimentos en Chile

BACKGROUND Foodborne disease outbreaks are one of the main health problems globally, having an extensive impact on human welfare. The World Health Organization considers them as the main cause of morbidity and mortality in developing countries, and responsible for high levels of loss of productivity in developed countries. AIM To describe the epidemiology of foodborne disease outbreaks according to data contained in an automated surveillance system. METHOD Descriptive observational study of notified outbreaks from the surveillance system, between 2005 and 2010 in Chile. The information was based on etiology, temporal and spatial distribution, and epidemiologic description of outbreaks during this period. RESULTS There were 5,689 notified outbreaks. Most of them occurred during 2006 (1,106 outbreaks, rate 6.7 per 100,000 inhabitants) and 2008 (1,316 outbreaks, rate 7.9 per 100, 000 inhabitants) with an increase during summer. Fifty four percent occurred in the Metropolitan region. The group aged 15 to 44 years old, was the most affected one. Sixty four percent of the outbreaks had the food involved registered, of which fish and fishery products reached 42%. An 81% of the outbreaks did not have a precise etiologic diagnosis. Of all patients involved, 97% were outpatients, 3,2% were hospitalized patients, and 0,1% died. Only 49% of the outbreaks had information about the lack of food safety, with a 34,1% related to food handling procedures. CONCLUSIONS Through the information on the epidemiology of foodborne diseases obtained by the Chilean surveillance system, appropriate control measures could be taken.Antecedentes: Las enfermedades transmitidas por alimentos (ETA) son una importante carga de enfermedad en el mundo. La OMS las senala como la principal causa de enfermedad y muerte en paises en desarrollo, mientras que en paises desarrollados son responsables de altos niveles de perdida de productividad. Objetivo: Describir epidemiologicamente los brotes de ETA chilenos de acuerdo a la informacion contenida en un sistema automatizado de vigilancia. Metodo: Estudio observacional descriptivo de los brotes notificados en el sistema de vigilancia, entre los anos 2005 y 2010 en Chile. La descripcion se baso en el aspecto etiologico, distribucion temporal y espacial, y descripcion epidemiologica de los brotes durante dicho periodo. Resultados: Se notificaron 5.689 brotes. La mayoria se presento durante el 2006 (1.106 brotes, tasa 6,7 por 100.000 hab) y 2008 (1.316 brotes, tasa 7,9 por 100.000 hab) con un aumento en los meses de verano. El 54% ocurrio en la Region Metropolitana. El grupo de 15 a 44 anos fue el mas afectado. Del 64% que registro el alimento involucrado, pescados y productos de la pesca alcanzaron el 42%. Un 81% del total de brotes no tuvo un diagnostico etiologico preciso. Del total de pacientes, 97% fueron ambulatorios, 3,2% se hospitalizaron, y 0,1% fallecieron. Solo 49% de los brotes registro perdida de inocuidad del alimento, siendo el mayor porcentaje (34,1%) atribuible al proceso de manipulacion del alimento. Conclusiones: El sistema de vigilancia chileno permitio conocer el comportamiento epidemiologico de las ETA, y facilito la adopcion de medidas de control oportunas.

Age as risk factor for death from pandemic (H1N1) 2009, Chile.

Pandemic (H1N1) 2009 affected Chile during the winter of 2009. The hospitalization rate was 0.56% overall and 3.47% for persons >60 years of age at risk for severe disease and death independent of concurrent conditions. Age >60 years was the major risk factor for death from pandemic (H1N1) 2009.

Tuberculosis in prisoners and their contacts in Chile: estimating incidence and latent infection.

SETTING Contact investigation of tuberculosis (TB) patients in Chilean prisons. OBJECTIVE 1) To estimate TB incidence and the prevalence of latent tuberculous infection (LTBI) among prisoners and their contacts; and 2) to determine factors associated with disease transmission. DESIGN Cross-sectional study conducted in 46 prisons (51% of the total prison population) to assess the prevalence of and risk factors for LTBI among contacts of prisoners newly diagnosed with pulmonary TB. We used in vitro interferon-gamma release assays to establish LTBI and a questionnaire to address risk factors. RESULTS During the 1-year follow-up, we studied 418 contacts of 33 active TB cases. We found high TB incidence (123.9 per 100,000 prisoners) and high LTBI prevalence (29.4%) among contacts. LTBI rates are significantly higher in prison inmates than in non-prisoners (33.2% vs. 15.6%). Male sex, illicit drugs, malnutrition, corticosteroid use, low educational level and sharing a cell with a case increase the risk of LTBI. Multivariate analyses showed that corticosteroid use, duration of incarceration and overcrowding are the most relevant determinants for LTBI among all contacts. CONCLUSIONS Our results confirm that incarceration increases the risk of tuberculous infection and TB disease, and that it was associated not only with origin from vulnerable groups, but also with the prison environment. Reinforcing TB control is essential to prevent TB transmission in prisons.