Uso de la herramienta Google Trends para estimar la incidencia de enfermedades tipo influenza en Argentina / Using Google Trends to estimate the incidence of influenza-like illness in Argentina / Uso da ferramenta Google Trends para estimar a incidência de síndrome gripal na Argentina

El objetivo del presente estudio fue hallar un modelo para estimar la incidencia de enfermedades tipo influenza (ETI), a partir de los términos de búsqueda relacionados recolectados por el Google Trends (GT). Los datos de vigilancia de ETI para los años 2012 y 2013 se obtuvieron del Sistema Nacional de Vigilancia de la Salud de Argentina. Las búsquedas de Internet se obtuvieron de la base de datos del GT, usando 6 términos: gripe, fiebre, tos, dolor de garganta, paracetamol e ibuprofeno. Se desarrolló un modelo de regresión de Poisson a partir de datos del año 2012, y se validó con datos del 2013 y resultados de la herramienta Google Flu Trends (GFT). La incidencia de ETI del sistema de vigilancia presentó fuertes correlaciones con las estimaciones de ETI del GT (r = 0,927) y del GFT (r = 0,943). Sin embargo, el GFT sobreestimó el pico de incidencia por casi el doble, mientras que el modelo basado en el GT subestimó el pico de incidencia por un factor de 0,7. Estos resultados demuestran la utilidad del GT como un complemento para la vigilancia de la influenza.

The aim of this study was to find a model to estimate the incidence of influenza-like illness (ILI) from the Google Trends (GT) related to influenza. ILI surveillance data from 2012 through 2013 were obtained from the National Health Surveillance System, Argentina. Internet search data were downloaded from the GT search engine database using 6 influenza-related queries: flu, fever, cough, sore throat, paracetamol, and ibuprofen. A Poisson regression model was developed to compare surveillance data and internet search trends for the year 2012. The model's results were validated using surveillance data for the year 2013 and results of the Google Flu Trends (GFT) tool. ILI incidence from the surveillance system showed strong correlations with ILI estimates from the GT model (r = 0.927) and from the GFT tool (r = 0.943). However, the GFT tool overestimates (by nearly twofold) the highest ILI incidence, while the GT model underestimates the highest incidence by a factor of 0.7. These results demonstrate the utility of GT to complement influenza surveillance.

O objetivo deste estudo foi encontrar um modelo para estimar a incidência da síndrome gripal com base nos termos de busca relacionados recolhidos pelo Google Trends (GT). Os dados de monitoramento de síndrome gripal entre 2012 e 2013 foram obtidos no Sistema Nacional de Vigilância de Saúde da Argentina. As pesquisas na Internet foram feitas baseando-se no banco de dados do GT usando 6 termos: gripe, febre, tosse, dor de garganta, paracetamol e ibuprofeno. Um modelo de regressão de Poisson foi desenvolvido valendo-se de dados de 2012. O modelo foi ajustado e validado com dados de 2013 e comparado com os resultados da ferramenta Google Flu Trends (GFT). A incidência de síndrome gripal mostrou uma forte correlação com estimativas do GT (r = 0,927) e GFT (r = 0,943). No entanto, o GFT superestimou o pico de incidência por quase o dobro, e o modelo baseado no GT subestimou o pico de incidência por um fator de 0,7. Esses resultados demonstram a utilidade do GT como um suplemento para a vigilância da influenza.

Cost-effectiveness of prevention strategies for American tegumentary leishmaniasis in Argentina / Custo-efetividade de estratégias de prevenção contra a leishmaniose tegumentar americana na Argentina / Coste-efectividad de estrategias de prevención contra la leishmaniasis tegumentaria americana en Argentina

The aim of this study was to estimate the cost-effectiveness of reducing tegumentary leishmaniasis transmission using insecticide-impregnated clothing and curtains, and implementing training programs for early diagnosis. A societal perspective was adopted, with outcomes assessed in terms of costs per disability adjusted life years (DALY). Simulation was structured as a Markov model and costs were expressed in American dollars (US$). The incremental cost-effectiveness ratio of each strategy was calculated. One-way and multivariate sensitivity analyses were performed. The incremental cost-effectiveness ratio for early diagnosis strategy was estimated at US$ 156.46 per DALY averted, while that of prevention of transmission with insecticide-impregnated curtains and clothing was US$ 13,155.52 per DALY averted. Both strategies were more sensitive to the natural incidence of leishmaniasis, to the effectiveness of mucocutaneous leishmaniasis treatment and to the cost of each strategy. Prevention of vectorial transmission and early diagnosis have proved to be cost-effective measures.

O objetivo deste estudo foi estimar o custo-efetividade para reduzir a transmissão da leishmaniose tegumentar americana, utilizando roupas e cortinas impregnadas com inseticidas e implementando programas de treinamento para o diagnóstico precoce. Adotou-se uma perspectiva social, usando os anos de vida ajustados por incapacidade (AVAI). Estruturou-se uma simulação com o modelo de Markov. Os custos foram expressos em US$. A taxa de custo-efetividade incremental foi calculada para cada estratégia. Foi desenvolvida análise de sensibilidade, uni e multivariada. A taxa de custo- efetividade incremental para o diagnóstico precoce foi estimada em US$ 156,46 por AVAI evitado, enquanto a taxa para prevenção com roupas e cortinas impregnadas foi de US$ 13.155,53 por AVAI evitado. Ambas as estratégias foram mais sensíveis à incidência natural de leishmaniose, à efetividade do tratamento contra a leishmaniose mucocutânea e ao custo de cada estratégia. A prevenção da transmissão vetorial e o diagnóstico precoce provaram ser medidas custo-efetivos.

El objetivo de este estudio fue estimar el coste-efectividad de reducir la transmisión de la leishmaniasis tegumentaria americana utilizando ropas y cortinas impregnadas con insecticidas, e implementando programas de entrenamiento para el diagnostico temprano. Se adoptó una perspectiva social, utilizando los años de vida ajustados por discapacidad (AVAD). Se estructuró una simulación con un modelo de Markov. Los costes fueron expresados en dólares americanos (US$). La razón de coste-efectividad incremental fue calculada para cada estrategia. Se desarrollaron análisis de sensibilidad de una vía y multivariados. La razón de coste-efectividad incremental para el diagnóstico temprano fue estimada en US$ 156,46 por AVAD evitado, mientras que la razón de coste-efectividad incremental para la prevención con ropa y cortinas impregnadas fue de US$ 13.155,52 por AVAD evitado. Ambas estrategias fueron más sensibles a la incidencia natural de leishmaniasis, a la efectividad del tratamiento contra leishmaniasis mucosa y al coste de cada estrategia. La prevención de la transmisión vectorial y el diagnóstico temprano han probado ser medidas coste-efectivas.

Nuevo método para elaborar corredores endémicos / New method for determining endemic levels

OBJETIVO: Diseñar un instrumento para elaborar corredores o canales endémicos mediante cálculos sencillos y, en el caso de enfermedades transmisibles, identificar y estimar parámetros relacionados con la dinámica de la transmisión. MÉTODOS: Se obtuvieron parámetros para elaborar una curva teórica de incidencia esperada, basada en el modelo logístico de crecimiento. Los parámetros se estimaron por medio de una regresión no lineal, a partir de datos de incidencia acumulada de los cinco años anteriores. Se tomó como ejemplo la incidencia semanal acumulada de casos de enfermedad tipo influenza para Argentina en 2009 y se la comparó con la serie de casos de 2004 a 2008 para construir los canales endémicos acumulados y no acumulados. RESULTADOS: De acuerdo a los canales endémicos acumulados obtenidos, el país entró en zona de brote a partir de la semana dos. El máximo número esperado de casos o capacidad de carga (K) de acuerdo a los datos de años previos fue de 1 090 660. Considerando los corredores no acumulados, la situación de brote se presentó en 34 de las 51 semanas. Se estimó un rango para la tasa básica de reproducción (R0) de 1,05 a 1,13 para el período no epidémico 2004-2008. CONCLUSIONES: El nuevo método permitió elaborar canales endémicos de una manera sencilla, con la obtención de parámetros importantes para la transmisión. Si bien tiene limitaciones, entre ellas que la ecuación utilizada es más útil para evaluar enfermedades con un ciclo anual marcado y menos exacta para ciclos menores de un año, puede ser considerado como una alternativa valiosa para elaborar corredores endémicos y una nueva contribución al estudio de brotes epidémicos en los niveles locales de vigilancia de la salud.

OBJECTIVE: Design an instrument for determining endemic levels or ranges using simple calculations; identify and estimate the parameters related to the dynamic transmission of communicable diseases. METHODS: The parameters for establishing a theoretical curve of expected incidence based on the logistic growth model were identified. The parameters were estimated by nonlinear regression based on the cumulative incidence data from the previous five years. The weekly cumulative incidence of cases of influenza-like illness in Argentina in 2009 was used as an example. It was compared to the 2004-2008 case series in order to determine the cumulative and non-cumulative endemic levels. RESULTS: According to the cumulative endemic levels identified, the country entered the outbreak area in week 2. The data from previous years showed that the maximum expected number of cases or carrying capacity (K) was 1 090 660. When the non-cumulative levels were considered, the outbreak was present in 34 out of 51 weeks. A range of 1.05 to 1.13 was estimated for the basic reproductive rate (R0) in the non-epidemic period from 2004-2008. CONCLUSIONS: The new method facilitated the determination of endemic levels using a simple procedure with the identification of parameters that are important for transmission. Although it has limitations such as the fact that the equation used is more appropriate for evaluating diseases with a pronounced annual cycle and less accurate for cycles of less than 1 year, it can be considered a valuable alternative method for determining endemic ranges and a new contribution to the study of epidemic outbreaks at local health surveillance levels.

Efecto del cierre de las escuelas sobre el brote de influenza A H1N1 en Tierra del Fuego, Argentina / Impact of school closings on the influenza A (H1N1) outbreak in Tierra del Fuego, Argentina

Se evaluó el efecto del cierre de las escuelas en la reducción del número de casos de enfermedades del tipo influenza durante un brote de influenza A por el virus H1N1, de características pandémicas, en las dos principales ciudades de la provincia de Tierra del Fuego, en la región austral de Argentina, en conjunto con otras medidas de control. Se comparó la incidencia antes y después del cierre de las escuelas en 2009 mediante la prueba de la t para muestras relacionadas. Hasta la semana 40 se detectaron 6 901 casos de enfermedades del tipo influenza, de ellos 281 se confirmaron como influenza A H1N1 mediante pruebas de laboratorio; 38 pacientes recibieron hospitalización. Se observó una reducción de cerca de 10 veces en la incidencia promedio registrada en los centros de salud después de la intervención. Los resultados indican que el cierre de las escuelas durante el brote de influenza A H1N1 se acompañó de una reducción significativa de la incidencia de enfermedades tipo influenza, aunque no se debe descartar el efecto de otras acciones, como el tratamiento de los casos y la profilaxis de sus contactos. Esta intervención, aplicada oportunamente, junto con otras medidas, puede contribuir a reducir la propagación de los brotes de influenza."

The impact of school closings on reducing the number of cases of influenza-like illness during an outbreak of influenza A (H1N1), which reached pandemic proportions, was assessed, along with other control measures, in the two main cities of Tierra del Fuego Province in southern Argentina. The incidence before and after the school closings in 2009 was compared by means of the t-test for related samples. By week 40, 6 901 cases of influenza-like illness had been detected, 281 of which were confirmed as influenza A (H1N1) through laboratory tests; 38 patients were hospitalized. After the intervention, there were nearly 10 times fewer cases than the average recorded in the health centers. The results indicate that closing schools during the influenza A (H1N1) outbreak resulted in a significantly lower incidence of influenza-like illness. However, the impact of other measures, such as case management and protection against exposure, should not be ignored. Timely implementation of this intervention, together with other measures, can help minimize the spread of influenza outbreaks.

Análisis costo-beneficio del control de vectores en la transmisión potencial de dengue / Cost-benefit analysis of vector control in areas of potential dengue transmission

OBJETIVOS: Evaluar el costo-beneficio de una intervención de control de mosquitos adultos con fumigación, junto con actividades de control de formas inmaduras de Aedes aegypti, para evitar la transmisión en una situación de alto riesgo. MÉTODOS: Se realizó un análisis de costo-beneficio desde una perspectiva social. Se comparó una intervención para el control de mosquitos adultos y formas inmaduras contra una hipótesis de no-intervención, de enero a abril de 2007, en la ciudad de Clorinda, Argentina. Se consideraron los costos directos y los beneficios indirectos e intangibles, estandarizados a dólares internacionales (I$) utilizando la paridad de poder adquisitivo. Se asumió una incidencia de 50 casos de dengue por 1 000 habitantes en la hipótesis de no-intervención. RESULTADOS: De enero a abril de 2007 se presentaron 176 casos de dengue en Clorinda, pero sólo cinco fueron autóctonos. El valor presente neto fue de I$ 196 879 en la estrategia de aplicación de control, mientras que en la de no aplicación se calculó en I$ -106 724, lo que significaría un ahorro de I$ 303 602 (I$ 6,46 por habitante) con la intervención. El análisis de sensibilidad evidenció que, con más de 1 363 casos de dengue (incidencia total de 29 por 1 000 habitantes) y un caso de dengue hemorrágico, la intervención es costo-benéfica. CONCLUSIONES: Los resultados sugieren que el control vectorial, incluyendo la fumigación para mosquitos adultos, debe evaluarse en situaciones de alto riesgo de transmisión como una alternativa costo-benéfica en países no endémicos.

OBJECTIVES: To evaluate the cost-benefit of an intervention utilizing fumigation against adult mosquitoes along with actions to control immature Aedes aegypti to prevent transmission in a high-risk area. METHODS: A cost-benefit analysis was performed from the social perspective. A program to control both adult mosquitoes and immature forms was compared to a non-intervention hypothesis, from January to April 2007, in the city of Clorinda, Argentina. Direct costs, as well as indirect and intangible benefits, were taken into account and standardized in international dollars (I$) using purchasing power parity. An incidence rate of 50 cases of dengue per 1 000 inhabitants was used in the non-intervention hypothesis. RESULTS: From January to April 2007 there were 176 cases of dengue in Clorinda, but only five were autochthonous. The net present value was I$ 196 879 with the control strategy, whereas the non-intervention was calculated to be I$ -106 724, indicating a savings of I$ 303 602 (I$ 6.46 per inhabitant) for the intervention. The sensitivity analysis showed that, with more than 1 363 cases of dengue (total incidence rate of 29 per 1 000 inhabitants) and one case of dengue hemorrhagic fever, there is a cost-benefit to intervention. CONCLUSIONS: The results suggest that vector control, including fumigation of adult mosquitoes, should be considered in high-risk areas as a cost-effective option for non-endemic countries.

Tegumentary leishmaniasis outbreak in Bella Vista City, Corrientes, Argentina during 2003

Bella Vista City, Corrientes, Argentina, reported an epidemic outbreak of tegumentary leishmaniasis during 2003. The mean age of the 31 cases was 25.0 ± 13.7 years old, with a sex ratio male:female 1.8, and without mucosal involvement. They clustered in two contiguous neighbourhoods, 96 percent in the periurban border and 4 percent in the peripheral outskirts. The transmission peak was estimated to have occurred during April 2003. Four species (3608 sand flies) were captured in nine sites: Lutzomyia neivai (90.1 percent), Lu. pessoai (8.9 percent), Lu. migonei (0.8 percent), and Brumptomyia avellari (0.2 percent). The outskirts/rural capture ratio of Lu. neivai was up to 3, and the outskirts/periurban up to 200. Therefore, the 'urban' transmission in this southernmost known focus is still an ecotone-border associated risk. The changes in human distribution or activities, patches of the secondary vegetation, periurban streams, rainfall of the previous year, and river period floods could all contribute to 'urban' outbreaks in the region. Tegumentary leishmaniasis risk should be assessed for any project that involves changes in land use throughout an endemic area.

Phlebotominae spatial distribution asssociated with a focus of tegumentary leishmaniasis in Las Lomitas, Formosa, Argentina, 2002

Las Lomitas, Formosa, Argentina, reported 96 cases of tegumentary leishmaniasis during 2002. The urban transmission was suggested although previous outbreaks were related with floods of the Bermejo river (BR) 50 km from the village. Phlebotomine collections were performed during March 2002 to define the spatial distribution of risk, together with satellite imaginery. The phlebotomine/trap obtained was 1679.5 in the southern BR shore, 1.1 in the periruban-rural environment and 2.3 in the northern Pilcomayo river marshes. Lutzomyia neivai was the prevalent species (91.1 percent) among the 2393 phlebotomine captured, and it was only found in the BR traps. The other species were L. migonei (7.9 percent), L. cortelezzii (0.9 percent), and Brumptomyia guimaraesi (0.1 percent). The satellite images analysis indicates that the fishing spots at the BR were significantlyoverflowed during the transmission peak, consistent with fishermen recollections. This spatial restricted flood might concentrate vectors, reservoirs, and humans in high places. Therefore, both the spatial distribution of vectors and the sensor remoting data suggests that in Las Lomitas area the higher transmission risk it is still related with the gallery forest of the BR, despite of the urban residence of the cases. The surveillance and control implications of these results are discussed.