Effects of extreme precipitation to the distribution of infectious diseases in Taiwan, 1994-2008

Abstract

The incidence of extreme precipitation has increased with the exacerbation of worldwide climate disruption. We hypothesize an association between precipitation and the distribution patterns that would affect the endemic burden of 8 infectious diseases in Taiwan, including water- and vector-borne infectious diseases. A database integrating daily precipitation and temperature, along with the infectious disease case registry for all 352 townships in the main island of Taiwan was analysed for the period from 1994 to 2008. Four precipitation levels, <130 mm, 130-200 mm, 200-350 mm and >350 mm, were categorized to represent quantitative differences, and their associations with each specific disease was investigated using the Generalized Additive Mixed Model and afterwards mapped on to the Geographical Information System. Daily precipitation levels were significantly correlated with all 8 mandatory-notified infectious diseases in Taiwan. For water-borne infections, extreme torrential precipitation (>350 mm/day) was found to result in the highest relative risk for bacillary dysentery and enterovirus infections when compared to ordinary rain (<130 mm/day). Yet, for vector-borne diseases, the relative risk of dengue fever and Japanese encephalitis increased with greater precipitation only up to 350 mm. Differential lag effects following precipitation were statistically associated with increased risk for contracting individual infectious diseases. This study's findings can help health resource sector management better allocate medical resources and be better prepared to deal with infectious disease outbreaks following future extreme precipitation events.

Figure 1. Risk maps of the 8 climate-related infectious diseases following extreme precipitation events were generated when the analysis was integrated with the GIS system.

The townships that had a significant association between the outbreak of the specified disease with the category of extreme precipitation events are marked on each map. Townships that had significant associations with heavy precipitation are marked in light purple, with torrential precipitation are marked in purple, while those that only had significant associations with extreme torrential precipitation are marked in dark purple.

Figure 2. Distribution of daily mean precipitation (in mm after Typhoon Nari) and the individual cases of bacillary dysentery with a 7-day lag after Typhoon Nari, 2001.

Figure 3. Case distribution of melioidosis after Typhoon Haitang, 2005.

There were 40 cases in southern Taiwan after Typhoon Haitang. 97.5% cases resided in the flooded areas and 70% of cases were in proximate contact of mud or flooding waters.