Fig 1.
Seasonality of dengue in Singapore: boxplot of monthly percent of cases (1983–2015).
Fig 2.
A) Mean daily intensity of rainfall in Singapore per a rainy day (1983–2011). The intensity is calculated by dividing amount of rainstorms by rainy days of a month. B) Mean duration of a dry period (i.e. sum of hourly stretches without rainfall) without a rainstorm. C) Monthly average numbers of rainy days; notice February is the driest month with only eight rainy days. Arrows indicate the Northeast (i.e. the wet and dry phases, NE1 and NE2, respectively) and Southwest (SW) monsoons. Data source: Changi station—National Environmental Agency (NEA).
Fig 3.
A descriptive sketch for the rainfall flushing mechanism shows how intense rainstorms during the monsoon results in washing breeding of dengue vector from stagnant drains.
Fig 4.
The study area: Geylang neighborhood, Singapore.
The figure shows locations of positive breeding sites for Aedes aegypti, Ae albopictus and Culex spp. Breeding drains of Ae. aegypti are given serial numbers that also used in Fig 6.
Table 1.
Total number of inspected and positive habitats in Geylang August 2014–August 2015.
Fig 5.
Monthly ratio of wet/dry habitats in Geylang (August 2014–August 2015).
Total numbers of inspected habitats are shown above bars. Arrows indicate periods of the wet and dry phases of the Northeast monsoon (NE1 and NE2, respectively) and Southwest monsoon (SW). Note: no inspections were carried out between 2/21/15 and 3/10/15.
Fig 6.
Timeline of the breeding drains of Aedes aegypti in Geylang, Singapore: August 2014- August 2015.
(SP: stagnant and positive, DN: Dry and Negative, SN: Stagnant and Negative, FN: Flushed and Negative). Grids along the x-axis represent the twice-weekly follow-ups. White grids indicate no inspections were carried out in these drains (two weeks between 2/21/2015 and 3/10/2015). Locations of the breeding drains are shown in Fig 4.
Fig 7.
A. Intensity of daily rainstorms in Geylang (August 2014–August 2015). B. Increase of water level in a drain in Geylang (August 2014–August 2015). C. larval density of Aedes aegypti per an outdoor breeding habitat in Geylang per semiweekly survey. D. Pupal-productivity of drains and non-drains for Ae. aegypti per semiweekly survey. Note: no monitoring was carried out between 2/21/2015 and 3/10/2015.