Singapore has reported more than 3,400 dengue fever cases since the beginning of the year and experts say that this number could increase 10-times in 2016 due to a number of factors.
The Singapore Health Ministry says the number of dengue cases in 2016 may exceed 30,000 – higher than the record in 2013 when 22,170 cases were reported, unless immediate measures are taken to suppress the Aedes mosquito population.
The following factors may contribute to this possible increase:
The El Niño weather phenomenon is the likely driver of the unusual high incidence of dengue cases at the start of 2016, outside of the typical dengue season. Studies have shown that El Niño events drive up the incidence of dengue on the global and regional scale. The warmer conditions due to the 2015 El Niño phenomenon support faster breeding and maturation cycles of the Aedes mosquitoes, and accelerate the multiplication of dengue viruses in mosquitoes.
The National Environmental Agency’s Gravitrap data has shown an increase in the Aedes aegypti mosquito population since November 2015. Compared to the same period in January 2015, 50 per cent more Aedes aegypti mosquitoes have been observed.
Additionally, the proportion of dengue cases due to the DENV-2 virus serotype has increased, replacing DENV-1 as the dominant virus and now accounts for about two-thirds of all dengue cases serotyped in Singapore. Historically, any change in predominant dengue virus serotype is usually followed by a spike in dengue cases.
This change in the main circulating dengue virus and the increase in mosquito population due to warmer temperatures may be contributing to the spike in dengue cases. Against a backdrop of low herd immunity amongst Singapore residents against dengue, the above development signals the increased possibility of a dengue outbreak in Singapore in 2016.