Description and lessons learned from the 2014 Dengue outbreak in Dar es Salaam, Tanzania. Knowledge, attitudes and bite prevention practices among those with confirmed Dengue

Background The frequency and magnitude of Dengue epidemics have increased dramatically in the past 40 years throughout the tropics largely due to unplanned urbanization, globalization and lack of effective mosquito control. Dar es Salaam, Tanzania has recently experienced Dengue outbreaks that occur with increasing frequency. Currently, only one serotype is recorded. Without adequate vector monitoring and control, it is certain that further outbreaks will occur. Methods/Findings A retrospective study followed 100 individuals with confirmed Dengue fever in Kinondoni, Dar es Salaam during the 2014 outbreak. Houses were inspected for mosquito breeding sites and gathered information on Socio-economic Status (SES) and Dengue prevention knowledge. Higher SES tertile had the most Dengue cases: 53 (55%) followed by medium and lower SES with 33 (34%) and 11 (11%) respectively. The highest number of mosquito breeding sites was also found in higher SES households. Kinondoni wards of Manzese, Mwananyamala, Tandale and Mabibo had the highest number of confirmed cases: 18, 13, 13 and 9 respectively. Each ward has large marketplaces, which may have aided dissemination of transmission to other areas. The population remains poorly informed about Dengue transmission: 22% of respondents said Dengue is spread from person to another, 30% did not think mosquitoes spread Dengue and 60% heard about Dengue while in hospital. Knowledge of bite prevention was poor; Dengue mosquito bites outside of sleeping hours but 84% of Dengue patients said that using bednets would prevent vector bites. Conclusion Affluent households are likely to be reservoirs of Dengue vectors having more breeding sites and Dengue cases. Mobile phones whose ownership is high across all social classes seem to be a better tool to communicate information about Dengue. The study established a habitat suitability score, a tool to be used for learning and estimate breeding habitat capacity to be used for vector control before rains begin. Author’s Summary Dengue fever is a viral infection transmitted by Aedes (Stegomyia) mosquitoes causing a flu-like illness that may develop into severe complications such as Dengue haemorrhagic fever and Dengue shock syndrome if the patient contracts two viral serotypes concurrently. There is currently no antiviral treatment or vaccines available against Dengue. Environmental vector control and mosquito bite prevention remain essential to prevent transmission. Due to globalisation and rapid urban expansion, Dar es Salaam is experiencing regular Dengue outbreaks. Without adequate vector control and public awareness, it is certain that these will continue to re-occur. The study presents factors associated with the outbreak in 2014. Rich households have more places for mosquitoes to breed with 54% found in these households and the majority of Dengue cases 55% came from higher SES groups that represented a greater proportion of cases than lower and middle socioeconomic groups, combined. The public was ill-informed about Dengue fever: 84% think bed nets can prevent Dengue, and 60% of the patients only became aware of Dengue while in the hospital with the illness. The study established a habitat suitability score, a tool to be used to estimate breeding habitat capacity before rains begin. Scattered containers especially tyres remain ideal breeding sites. The study highlights the need for waste management to avert future outbreaks.