Contact tracing, with indoor spraying, can curb dengue outbreak

February 17, 2017
An airy, traditional Queenslander style house in Cairns, Australia, is open to the breezes, but also to mosquitoes. Credit: James Cook University

Contact tracing, combined with targeted, indoor residual spraying of insecticide, can greatly reduce the spread of the mosquito-borne dengue virus, finds a study led by Emory University.

In fact, this novel approach for the surveillance and control of fever—spread by the same mosquito species that infects people with the Zika virus—was between 86 and 96 percent effective during one outbreak, the research shows. By comparison, vaccines for the dengue virus are only 30-to-70-percent effective, depending on the serotype of the virus.

Science Advances published the findings, which were based on analyses from a 2009 outbreak of dengue in Cairns, Australia.

"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. "We've also shown the importance of human movement when conducting surveillance of these diseases."

"The United States is facing continual threats from dengue, chikungunya and Zika viruses," says Sam Scheiner, director of the National Science Foundation's Ecology and Evolution of Infectious Diseases Program, which funded the research. "For now, the response is to intensively spray insecticides. This research shows that a more targeted approach can be more effective."

While the method would likely not be applicable everywhere, Vazquez-Prokopec says that it may be viable to control Aedes-borne diseases in places with established health systems and similar environmental characteristics to Cairns, such as South Florida or other U.S. states at risk of virus introduction.

"The widespread transmission of dengue viruses, coupled with the birth defects associated with Zika virus, shows the dire need for as many weapons as possible in our arsenal to fight diseases spread by these mosquitos," he says. "Interventions need to be context dependent and evaluated carefully and periodically."

During the dengue outbreak in Cairns, public health officials traced recent contacts of people with a confirmed infection - a surveillance method known as contact tracing. This method is commonly used for directly transmitted pathogens like Ebola or HIV, but rarely for outbreaks spread by mosquitos or other vectors.

Using mobility data from the known cases, public health workers targeted residences for indoor residual spraying, or IRS. Walls of the homes—from top to bottom—and dark, humid places were Aedes mosquitos might rest, were sprayed with an insecticide that lasts for months.

The method is time-consuming and labor intensive, and health officials were not able to reach all of the residences that were connected to the infected persons.

The researchers found that performing IRS in potential exposure locations reduced the probability of by at least 86 percent in those areas, in comparison to areas of potential exposures that did not have indoor spraying.

"The findings are important," Vazquez-Prokopec says, "because they demonstrate one of the few measures that we have for the effectiveness of an intervention to reduce the transmission of dengue."

Many times, he says, in the face of a dengue outbreak end up using trucks to spray insecticide—despite the lack of scientific evidence for the effectiveness of fogging from the streets to control Aedes aegypti mosquitos.

Quantifying the effectiveness of existing methods, and the context within which they work, can strengthen the vector-control arsenal. "We need to develop plans for outbreak containment that are context-specific," Vazquez-Prokopec says.

He is researching ways to scale up this intervention. While it now takes approximately half-an-hour to conduct indoor residual spraying in a single house, he would like to cut that time to as little as 10 minutes.

"We are evaluating how we can scale up and improve IRS for 21st-century urban areas," Vazquez-Prokopec says.

Explore further: Zeroing in on 'super spreaders' and other hidden patterns of epidemics

More information: "Combining contact tracing with targeted indoor residual spraying significantly reduces dengue transmission," Science Advances, advances.sciencemag.org/content/3/2/e1602024

Related Stories

Zeroing in on 'super spreaders' and other hidden patterns of epidemics

February 25, 2016
Ebola. Chikungunya. Zika. Once rare and exotic pathogens keep popping up and turning into household names. It's the new reality as the climate warms, humans expand more into wildlife habitats and air travel shrinks the distances ...

Chasing fire: Fever and human mobility in an epidemic

July 19, 2016
Disease ecologists working in the Amazonian city of Iquitos, Peru, have quantified for the first time how a fever affects human mobility during the outbreak of a mosquito-borne pathogen. The findings were published by Proceedings ...

Why Zika risk is low for Olympic athletes in Rio

July 8, 2016
Some health professionals have lobbied to postpone the upcoming Rio de Janeiro Olympics due to the risk of the Zika virus, which is spread by mosquitos and – less commonly – through sexual intercourse. Other experts disagree ...

Tracking the spread of dengue fever: Domestic networks drive rapid transmission of human infection

January 24, 2013
The mosquitoes that spread dengue fever tap into the domestic networks of humans, along with their bloodstreams, finds a study recently published in the Proceedings of the National Academy of Sciences (PNAS).

Vaccinating against dengue may increase Zika outbreaks

October 31, 2016
Vaccinating against dengue fever could increase outbreaks of Zika, suggests new research out of York University and Xi'an Jiaotong University in China.

Antibody test gauges mosquito exposure

December 1, 2016
How many mosquitoes live in your neighborhood? How many mosquito bites have you and your neighbors gotten this week? Answering these questions—and gauging how mosquito populations change over time or after a control strategy ...

Recommended for you

Portable 3-D scanner assesses patients with elephantiasis

October 17, 2017
An estimated 120 million people worldwide are infected with lymphatic filariasis, a parasitic, mosquito-borne disease that can cause major swelling and deformity of the legs, a condition known as elephantiasis. Health-care ...

New tools to combat kidney fibrosis

October 16, 2017
Interstitial fibrosis – excessive tissue scarring – contributes to chronic kidney disease, which is increasing in prevalence in the United States.

How hepatitis C hides in the body

October 13, 2017
The Hepatitis C (HCV) virus is a sly enemy to have in one's body. Not only does it manage to make itself invisible to the immune system by breaking down communication between the immune cells, it also builds secret virus ...

Largest study yet of malaria in Africa shows historical rates of infection

October 12, 2017
(Medical Xpress)—A team of researchers with members from the Kenya Medical Research Institute, the University of Oxford and the University of KwaZulu-Natal has conducted the largest-ever study of the history of malaria ...

Promising new target for treatment of psoriasis is safe, study shows

October 11, 2017
A protein known to play a significant role in the development of psoriasis can be prevented from functioning without posing a risk to patients, scientists at King's College London have found.

Norovirus evades immune system by hiding out in rare gut cells

October 11, 2017
Noroviruses are the leading cause of non-bacterial gastroenteritis in the world and are estimated to cause 267 million infections and 20,000 deaths each year. This virus causes severe diarrhea, nausea, and stomach pain.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.