Spatial and epidemiologic features of dengue in Sabah, Malaysia

In South East Asia, dengue epidemics have increased in size and geographical distribution in recent years. Most studies investigating dengue transmission and control have had an urban focus, while less consideration is currently given to rural settings, or where urban and rural areas overlap. We examined the spatiotemporal distribution and epidemiological characteristics of reported dengue cases in the predominantly rural state of Sabah, in Malaysian Borneo – an area where sylvatic and urban circulation of pathogens are known to intersect. We found that annual dengue incidence rates were spatially variable over the 7-year study period from 2010-2016 (state-wide mean annual incidence of 21 cases/100,000 people; range 5-42/100,000), but were highest in rural localities in the western districts of the state (Kuala Penyu, Nabawan, Tenom and Kota Marudu). The eastern districts exhibited lower overall dengue rates; however, we noted a concentration of severe (haemorrhagic) dengue cases (44%) in Sandakan and Tawau districts. Dengue incidence was slightly higher for males than females, and was significantly higher for both genders aged between 10 and 29 years (24/100,000; p=0.029). The largest ever recorded outbreaks occurred during 2015-2016, with the vector found to be most prevalent in both urban and rural households (House Index of 64%), compared with (15%). These findings suggest that dengue outbreaks in Sabah are driven by the sporadic expansion of dengue virus in both urban and rural settings. This may require tailoring of preventative strategies to suit different transmission ecologies across Sabah. Further studies to better understand the drivers of dengue in Sabah may aid dengue control efforts in Malaysia, and more broadly in South East Asia.