Mapping patient’s movements during an outbreak may be key to reducing dengue transmission

Photo Credit: CDC/James Gathany

When tackling diseases spread by mosquitoes it’s easy to forget that humans move around too.

A recent study investigating a dengue outbreak in Australia revealed that humans were important dispersers of dengue virus during an outbreak in Cairns in 2008 and 2009. In this study, patients were interviewed about their movements in order to locate and treat areas that were important hubs of dengue transmission in the city.

When controlling dengue outbreaks, health authorities traditionally use insecticide to spray inside the homes of people who have been clinically confirmed to have the virus. The drawback is that not everyone gets identified quickly or even develops symptoms.

Contact tracing can be a useful way of mapping and controlling outbreaks of infectious diseases like SARS or Ebola, but it is not often used when investigating diseases spread by mosquitoes like dengue or zika viruses.

This study set out to test whether contact tracing was a useful method of controlling outbreaks by using space-time statistical modelling to analyse the movements of over 900 people with laboratory confirmed dengue.

The researchers found that targeted indoor residual spraying of these transmission locations, identified by the movements of patients, reduced the probability of new dengue cases occurring by 86 to 96 percent compared to controls.

“We’ve provided evidence for a method that is highly effective at preventing transmission of diseases carried by the Aedes aegypti mosquito in a developed, urban setting,” says the study’s lead author, Gonzalo Vazquez-Prokopec, a disease ecologist in Emory’s Department of Environmental Sciences.

This method of finding important areas of virus transmission may potentially be useful when tackling other mosquito-borne diseases carried by Aedes mosquitoes, for example zika.

However, the author’s do state that more research is needed before this method can be used in other contexts and that it may not be a useful tool in countries where there is a poor public health infrastructure.

Want to learn more?

The original paper can be found here

More information about the Cairns dengue outbreak can be found here.

Some general background information about the ‘pandemic-prone’ dengue virus can be found here.

Information about the Aedes aegypti mosquito, the cockroach of mosquitoes, can be found here.

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