Featured Research

from universities, journals, and other organizations

Scientists testing early warning system for West Nile virus

Date:
October 31, 2012
Source:
South Dakota State University
Summary:
Using satellite imaging data from 2000 to the present, a scientist is testing an early warning system for West Nile virus risk in South Dakota. He predicted a high risk of West Nile virus for 2012, even though the state experienced a drought. And he was right.

Based on data from satellite imaging, Michael Wimberly, senior scientist at the Geographic Information Science Center of Excellence at South Dakota State University, predicted a high risk for West Nile virus in South Dakota during the 2012 season. Public health officials may one day rely on his forecasts to warn people to take precautions against contracting the virus.
Credit: Image courtesy of South Dakota State University

When weather radar shows a funnel cloud, the tornado sirens howl, and folks run for cover. With outbreaks of West Nile virus, it's not that simple.

Related Articles


Michael Wimberly, senior scientist at the Geographic Information Science Center of Excellence at South Dakota State University, has begun testing an early warning system for West Nile virus. Through a grant from the National Institute of Allergy and Infectious Diseases, Wimberly has analyzed satellite imaging data from 2000 to the present day to build a store of information to predict the future.

Key collaborators in this interdisciplinary effort include professor Mike Hildreth in biology and microbiology, associate professor Yi Liu in electrical engineering and computer science, and Ting-Wu Chuang, a former postdoctoral researcher now at Taiwan Medical University. Wimberly and Chuang recently published their findings on climatic variability and West Nile virus outbreaks in the northern Great Plains in the journal PLOS ONE.

"My first forecast in 2010 was completely wrong," he said. An early spring led to a prediction of an active year for West Nile virus, but the opposite was true.

"What we're doing is unique," Wimberly said. "We are trying to make a much tighter link from research to application." To do this, he has been working closely with the S.D. Department of Health and the state epidemiologist.

After his first attempt, Wimberly developed more sophisticated models and predicted a low risk of West Nile infections for 2011. This time he was right.

Temperature strong indicator

"Our research has shown if we look broadly at a regional level, temperature is an extremely strong driver," he said.

Wimberly found associations between West Nile virus and temperature at two different times of the year. First, an earlier spring green up, like this past year with the warm April, gives the virus a longer amplification period, he said. "In general, mosquitos develop more rapidly, are more active and tend to bite more when it's hotter."

Since the virus originates in the bird population but is transmitted to humans through a mosquito, an early spring alone is not a sufficient predictor. Wimberly explained that the Culex tarsalis mosquito must first bite an infected bird to acquire West Nile, and then the virus must incubate in the mosquito.

"The blood goes into the stomach," he said, but in order for the mosquito to transmit the disease, the virus must reach its salivary glands. This process is also temperature dependent.

"The warmer it gets, the shorter the amount of time it takes for the mosquitos to become infectious," Wimberly said. Consequently, a warmer than normal summer will accelerate the transmission from mosquitoes to humans.

In 2010, the population of the West Nile-carrying mosquitos was high, Wimberly explained. Yet the expected outbreak never occurred because of the cooler temperatures that summer. Despite the high mosquito numbers, very few were infected with the West Nile virus. Moisture, more complicated.

Determining the virus' relationship with moisture and rainfall is more complicated, Wimberly said. Mosquitoes need water to breed; therefore, people assume that areas experiencing a drought will have a reduced risk of West Nile virus.

"There is a tendency to assume a linear relationship with rainfall and mosquitos," Wimberly said, but it's more complex than that.

"Culex tarsalis are not flood water mosquitoes, so they don't respond to rainfall with a huge breeding generation," he said. The West Nile carriers are selective, preferring grass in roadside ditches, wheel ruts in a pasture, and irrigated alfalfa as a breeding ground. Wimberly called it the "Goldilocks effect--the water needs to be just right."

After dramatic declines in the incidence of West Nile in 2010 and 2011, some researchers thought the virus had become less virulent and was fading away, Wimberly explained. Others believed that the bulk of the population had already been infected without having major symptoms and were already immune.

Enter 2012, the deadliest West Nile season ever.

Wimberly submitted his forecast for 2012 before the season began, and using a temperature-driven model, he predicted a high risk for West Nile outbreaks in South Dakota. "You don't hope you're right; you don't want a disease outbreak," Wimberly said.

But he was right.

Model, a work in progress

Wimberly explained, "You fit a model, use it to make a forecast and put it out there and then evaluate the forecast and see where it's right and wrong." But to perfect the model, he said, "you have to be in the game for the long term."

To do this, Wimberly has applied to the National Institutes of Health for an extension of the four-year grant which began in 2008. His next step will be to incorporate more information to do risk mapping, identifying places where transmission risk is highest. "Over time, we get better," Wimberly said, and as a result, the public health community will begin to trust the forecasts.

Though sirens might not sound to warn about West Nile virus, Wimberly's forecasts may one day offer a warning to take precautions to avoid contracting the disease.


Story Source:

The above story is based on materials provided by South Dakota State University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Ting-Wu Chuang, Michael C. Wimberly. Remote Sensing of Climatic Anomalies and West Nile Virus Incidence in the Northern Great Plains of the United States. PLoS ONE, 2012; 7 (10): e46882 DOI: 10.1371/journal.pone.0046882

Cite This Page:

South Dakota State University. "Scientists testing early warning system for West Nile virus." ScienceDaily. ScienceDaily, 31 October 2012. <www.sciencedaily.com/releases/2012/10/121031110701.htm>.
South Dakota State University. (2012, October 31). Scientists testing early warning system for West Nile virus. ScienceDaily. Retrieved November 24, 2014 from www.sciencedaily.com/releases/2012/10/121031110701.htm
South Dakota State University. "Scientists testing early warning system for West Nile virus." ScienceDaily. www.sciencedaily.com/releases/2012/10/121031110701.htm (accessed November 24, 2014).

Share This


More From ScienceDaily



More Plants & Animals News

Monday, November 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Winter Can Cause Depression — Here's How To Combat It

Winter Can Cause Depression — Here's How To Combat It

Newsy (Nov. 23, 2014) Millions of American suffer from seasonal depression every year. It can lead to adverse health effects, but there are ways to ease symptoms. Video provided by Newsy
Powered by NewsLook.com
Ebola-Hit Sierra Leone's Late Cocoa Leaves Bitter Taste

Ebola-Hit Sierra Leone's Late Cocoa Leaves Bitter Taste

AFP (Nov. 23, 2014) The arable district of Kenema in Sierra Leone -- at the centre of the Ebola outbreak in May -- has been under quarantine for three months as the cocoa harvest comes in. Duration: 01:32 Video provided by AFP
Powered by NewsLook.com
Anglerfish Rarely Seen In Its Habitat Will Haunt You

Anglerfish Rarely Seen In Its Habitat Will Haunt You

Newsy (Nov. 22, 2014) For the first time Monterey Bay Aquarium recorded a video of the elusive, creepy and rarely seen anglerfish. Video provided by Newsy
Powered by NewsLook.com
Birds Around the World Take Flight

Birds Around the World Take Flight

Reuters - Light News Video Online (Nov. 22, 2014) An imperial eagle equipped with a camera spreads its wings over London. It's just one of the many birds making headlines in this week's "animal roundup". Jillian Kitchener reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins