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Lanka faces Zika threat, strict airport monitoring essential
View(s):The main vectors of the Zika virus are present across Sri Lanka and, as one of the most densely populated countries in the world, the risk of infection through mosquito bites or sexual transmission remains “a major concern”, researchers in Singapore warn.
“Should Zika not be currently present in Sri Lanka, it is highly likely in the near future that an importation event will occur,” say Dr. Borame Dickens and Dr Jie Yang. “Zika infection shows similar symptoms to dengue hence misdiagnosis is possible. Thus, under-reporting and a lack of surveillance could potentially explain why a Zika case has not been reported in Sri Lanka yet.”
The researchers are investigating the role of travel and climate in Zika dispersal as a co-project between the Department of Biological Sciences and Saw Swee Hock School of Public Health at the National University of Singapore.
“Aedes aegyptii and Aedes albopictus, thought to be the main vectors of the Zika virus, are both present across Sri Lanka owing to favourable climatic and anthropogenic conditions,” they told the Sunday Times in an email interview. “Persistent rainfall and limited vector control contribute towards the formation of stagnant pools of water, which provides ideal breeding sites for these mosquitoes.”
The recent floods have also heightened the danger. “It is well established that expanding surface water will inevitably increase the number of available breeding sites for mosquitoes,” Dr Dickens and Dr Jie say. “The risk of Zika transmission depends on the number of mosquitoes carrying the Zika virus in Sri Lanka. A greater mosquito population could elevate biting rates, and therefore increase the potential spread of Zika.”
Furthermore, temperatures all year round are ideal for mosquito reproduction, increasing the chance of interaction between mosquito and human hosts. As one of the most densely populated countries in the world, with more than 20 million people residing on a landmass of about 65,000km2, the risk of infection through either mosquito bites or sexual transmission remains a major concern.
The disease could also be asymptomatic, further increasing the chance of missing detection, the researchers point out. The main pathway of importation appears to be through air travel from areas of local Zika transmission. “To prevent the arrival of Zika, strict airport monitoring and quarantine measures must be implemented where suspected cases are detected,” they advise. “Individuals who have travelled to areas of local transmission should avoid sexual contact for up to 12 days, which is the incubation time for the Zika virus. If no symptoms develop after this period, it is generally considered safe to resume sexual activity.”
“However, if a person develops symptoms similar to dengue, they should be hospitalised,” they stress. “This requires public engagement and education to help the local population recognise and understand how Zika transmission can be prevented. Should mosquitoes carry Zika, a national campaign of traditional vector control methods using bed nets, fogging and the removal of stagnant pools of water is required to prevent the spread of Zika.”
International experts in public health and disease must be consulted throughout this process to ensure that this programme is implemented effectively. The potential application of an RIDL or Wolbachia campaign should also be considered.
Recent technologies advances in mosquito control have led to the development of RIDL (Release of Insects with Dominant Lethality) by OXITEC (UK) and Wolbachia infected mosquitoes by the Eliminate Dengue Project (Australia). Both projects aim to suppress wild mosquito populations through a targeted species-specific approach, which reduces the chance of being bitten by a Zika or dengue mosquito vector.
Cultural factors, health awareness and case locations will all play a role in how quickly it will potentially spread and the longer cases remain undiagnosed, the greater the chance of secondary cases occurring. With the already high level of uncertainty in the estimates of Zika case numbers, estimating spread will only become more difficult unless surveillance and detection increase significantly.