The spatial and temporal dynamics of dengue hemorrhagic fever incidence in Thailand.

摘要

An estimated 50--100 million people are afflicted by dengue fever each year. Two to five hundred thousand of these cases occur as the severe form of the disease, dengue hemorrhagic fever (DHF). The control measures that are currently available are mosquito control and case management of infections. In the near future, a vaccine may be available to protect people from the disease. There are obstacles to each of these control measures. The allocation of resources to current control techniques after the start of an epidemic rarely affects that epidemics course. Since the pattern of incidence is difficult to forecast and the resources available for control are limited, public health systems respond only at times when control measures are ineffectual. Vaccine programs suffer different obstacles. Before vaccines can be implemented at a national level, the effect of these programs on population wide transmission must be understood. This is difficult due to certain characteristics of the dengue virus, specifically, the risk posed to individuals experiencing their second infection.; This dissertation focuses on the obstacles to effective implementation of current and future control measures. Three studies are presented. The first study analyses the temporal patterns of DHF incidence and meteorological variables in Thailand to determine if the timing of these variables is associated. The results show that the timing of the dengue season is associated with the timing of the rainy season in Thailand. Also, we show that warmer years are associated with higher annual incidences in DHF.; The second study describes a periodic traveling wave in DHF incidence. This wave emanates from Bangkok and accounts for a large proportion of the interannual variance in DHF incidence in Thailand. The findings from these two studies can be used to build forecasts of DHF incidence in Thailand.; The final study presents a transmission model of dengue. The effect of vaccination programs is examined using this model. The results indicate that vaccination programs produce increases in secondary infections only for a small number of modeled vaccination programs. These results indicate characteristics of vaccines that should be studied carefully in order to avoid increases in incidence.