Climate change and dengue in Sri Lanka
Rising incidence of dengue in Sri Lanka is attributable to changing monsoon patterns
Dengue infection rates are seen to climb immediately after the monsoon season in September
Factors such as unplanned urbanisation, excess water supply and moving populations are also to blame
The recorded number of dengue cases in the island nation grew seven fold between 2008 aand 2014.
From a relatively low 6,660 infections in 2008, recorded cases of dengue jumped to 25,235 in 2009 with 249 fatalities. Infection rates have been on the rise with last year recording a five-year high of 47,000 infections. This year, so far, there have been over 19,000 infections and more are expected in the post-monsoon period after September.
“We have seen infections rising during the post-monsoon season, especially in the densely populated urban areas,” Paba Palihawadanda, head of epidemiology at the health ministry, tells SciDev.Net.
The Sri Lankan government now spends US$ 2 million dollars on dengue prevention programmes annually. The health ministry has been running a series of anti-dengue public campaigns, the latest running this month (10—16 September), in the hope of containing the spread of the mosquito-borne viral disease.
Research done at the University of Peradeniya and published in 2014 in the International Journal of Infectious Diseases had warned that "Climate (temperature, rainfall, and humidity) change due to global warming can expand the geographical range of vector mosquitoes, extend the disease transmission season, shorten the gonotrophic cycle, and reduce the time taken for ingested viruses to develop to infective stages in mosquitoes, thereby increasing the propagation rates of arboviral diseases transmitted."
Meanwhile, health experts at the Asian Development Bank (ADB) say that the correlation between dengue and rising temperatures is influenced by several factors, besides climate change.
"Even though we can see a link between changing climate patterns and the spread of dengue, the situation is exacerbated by other factors like unplanned urbanisation, water supply practices leading to standing water, and increased mobility of people,” says Susann Roth, social development specialist with the ADB.
An ADB publication released in 2014, titled Assessing the Costs of Climate Change and Adaptation in South Asia predicted that a two degree Celsius rise in global temperature working alongside other factors could see a ten-fold increase in Sri Lanka’s annual dengue infections and fatalities by 2090.
“We need more research to understand concretely the links between all these multiple factors that impact the spread of dengue,” Roth tells SciDev.Net.
This article has been produced by SciDev.Net's South Asia desk.