Study on the Weather Effects on Dengue and Dengue Surveillance System in Fiji

Background: Dengue is one of the most common vector transmitted diseases in the world and it has become a public health problem in many countries including Fiji. Efficient methods need to be taken for dengue prevention and control in Fiji. Disease surveillance is one of the most effective way for dengue prevention and idea of using weather parameters to estimate dengue cases as one part of dengue surveillance has been studied by different researchers worldwide. The study aimed to estimate the relationship between weather variables including rainfall, temperature and humidity and to identify problems existed in current surveillance system in Fiji. Methods: Both quantitative and qualitative methods were used in the study. In the quantitative study, disease data of dengue cases collected by Fiji National Notifiable Disease Surveillance System from Jan 2011 to Dec 2014 and weather data collected by meteorological station in Laucala Bay, Suva from Jan 2011 to Dec 2014 were provided by Fiji Ministry of Health. Disease data were divided into two parts, years with sporadic cases (Jan2011-Oct2013) and years with dengue outbreak (Nov2013-Dec2014), and negative binominal regression was conducted to estimate the association between weather variables including rainfall, maximum temperature, minimum temperature and relative humidity. In the qualitative study, in-depth interviews were conducted with health workers and dengue patients in Suva and evaluations of current surveillance system and problems being noticed in the surveillance system were discussed. Results: Statistically significant positive associations between weather variables including weekly cumulative rainfall and weekly average relative humidity and dengue cases were identified in years with sporadic cases. In years with dengue outbreak, weekly average maximum temperature and relative humidity were also found to be significantly positively associated with dengue cases. Average minimum temperature per week was found to be significantly negatively associated with dengue cases. Problems of timeliness, accuracy and completeness in dengue case report process were identified and inadequate public health awareness of health workers was also raised in the interviews. Conclusions: Weather variables including rainfall, temperature and humidity showed significant effects on variations of dengue cases. The significant associations between weather variables and dengue cases may establish the foundation of developing a climate-based early warning system for dengue in Fiji. Problems in the current surveillance system for dengue have been identified including lack of timeliness and compromised quality in the case reporting process. Web-based disease reporting system and standardized reporting procedures may be useful in improving the surveillance system. A more efficient disease surveillance system can be developed combining the effects of weather variations on the number of dengue cases and routine surveillance together.