Dengue hemorrhagic fever (DHF) is a potentially fatal manifestation of an infection with the mosquito-borne dengue virus. Because of the social and economic costs of DHF, many countries in Asia and South America have initiated public health measures aimed at vector control. Despite these measures, DHF incidence rates do not appear to be declining. The effectiveness of vector control in reducing dengue transmissibility has thereby been questioned. Here, we revisit this conclusion using epidemiological data from Thailand. We first show, with age incidence data, that dengue transmission rates have fallen since 1981; surprisingly, however, these declines are not associated with decreases in DHF incidence. Instead, district-level analyses indicate a nonmonotonic relationship between the basic reproductive number R 0 and DHF incidence. To understand this relationship, we formulated three mathematical models, which differ in their assumptions of transient between-serotype cross-protection. Unlike the first two models, the previously unconsidered third model with clinical cross-protection can reproduce this nonmonotonic relationship. Simulation of this model with nonstationary R 0 reproduces several previously unexplained patterns of dengue dynamics, including a transition from a Ϸ2-year cycle to a Ϸ4-year cycle and a transient trough in DHF incidence in provinces with rapid R 0 declines. These results imply that DHF incidence can be effectively controlled with a sufficiently large reduction in R 0 but that moderate reductions may be counterproductive. More broadly, these results show that assuming parameter stationarity in systems with approximate stationarity in disease incidence is unjustified and may result in missed opportunities to understand the drivers of disease variability.dengue dynamics ͉ interannual disease variability ͉ multistrain dynamics

SummaryAn intense epidemic of dengue haemorrhagic fever in 1998 prompted the Thai government to investigate the feasibility of focalized vector (Aedes aegypti) control programmes. We tested for correlations of three indices of Aedes larval abundance (housing index, container index and Breteau index) against 38 socio-economic and four climatic variables. Availability of public water wells, existence of transport services and proportion of tin houses were positively associated with larval indices. Private water wells, health education, health insurance coverage, thatched houses and use of firewood for cooking were negatively associated. These probably represent both direct effects on breeding sites (private vs. public wells decrease necessity to store water, and health education may encourage breeding site removal), and more general effects of health-related attitudes, housing quality and remoteness from urban areas. Indices were positively associated with daily minimum temperature, an increase in precipitation from the previous month (reflecting the onset of the rainy season) and daily maximum temperatures of approximately 33-34°C. The associations were used to derive statistical models to predict the rank order of larval indices within the study area (Spearman's correlation coefficients ¼ 0.525-0.554). The study provides a rational basis for identifying possible social interventions, and for prioritizing previously unsurveyed villages for further monitoring and focalized vector control.

PurposeTo determine the biochemical characteristics of lung cancer tissue using in vitro 1H‐MRS, and investigate the correlation between survival probabilities and lactate (Lac), creatine (Cr), and choline (Cho) concentrations measured by in vitro 1H‐MRS.Materials and MethodsA total of 21 patients with lung cancer were included in this retrospective study. 1H‐MRS spectra measurements were performed at 6.35T using a JNM‐EX270, high‐resolution FT‐NMR spectrometer.ResultsWhen normal lung tissue was compared with lung cancer tissue, significant differences were noted most consistently in the levels of Lac and Cho, with lung cancer tissue showing higher values than normal lung tissue. Lac concentrations of lung cancer tissue were significantly higher in patients with recurrence compared to patients without recurrence (0.285 ± 0.096 μmol/g). The mean overall survival of patients in the low‐Lac group was 50.28 ± 6.47 months, which is significantly higher compared to the high‐Lac group, which had a mean survival time of only 30.49 ± 5.41 months.ConclusionKaplan‐Meier analysis of the data showed that the overall and disease‐free survival probabilities were significantly higher in patients with low tumor Lac values than in those with high tumor Lac concentrations. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.

BackgroundDengue is the most prevalent mosquito-borne virus, and potentially fatal dengue hemorrhagic fever (DHF) occurs mainly in secondary infections. It recently was hypothesized that, due to the presence of cross-immunity, the relationship between the incidence of DHF and transmission intensity may be negative at areas of intense transmission. We tested this hypothesis empirically, using vector abundance as a surrogate of transmission intensity.Methodology/Principal FindingsHouse Index (HI), which is defined as the percentage of households infested with vector larvae/pupae, was obtained from surveys conducted on one million houses in Thailand, between 2002 and 2004. First, the utility of HI as a surrogate of transmission intensity was confirmed because HI was correlated negatively with mean age of DHF in the population. Next, the relationship between DHF incidence and HI was investigated. DHF incidence increased only up to an HI of about 30, but declined thereafter. Reduction of HI from the currently maximal level to 30 would increase the incidence by more than 40%. Simulations, which implemented a recently proposed model for cross-immunity, generated results that resembled actual epidemiological data. It was predicted that cross-immunity generates a wide variation in incidence, thereby obscuring the relationship between incidence and transmission intensity. The relationship would become obvious only if data collected over a long duration (e.g., >10 years) was averaged.ConclusionThe negative relationship between DHF incidence and dengue transmission intensity implies that in regions of intense transmission, insufficient reduction of vector abundance may increase long-term DHF incidence. Further studies of a duration much longer than the present study, are warranted.