A Speedy Test For Norovirus Could Help Water Supplies Check For Contamination
Friday, August 30, 2019
Norovirus tends to makes the news when an outbreak occurs on cruise ships. But the virus affects many more people than ocean-going vacationers.
The Centers for Disease Control and Prevention estimates some 20 million people suffer acute intestinal illness from norovirus each year in this country. It's responsible for more than half of all cases of foodborne illness in the United States.
It can also get into municipal water supplies, when old pipes or storm overflow cause waste water contaminated with the norovirus to mix with drinking water.
"When we have a massive outbreak related to drinking water quality there is a high probability that norovirus caused that infection," says environmental biologist Kelly Reynolds at the University of Arizona Mel and Enid Zuckerman College of Public Health in Tucson.
Water utilities regularly check for contamination, but Reynolds says existing tests for norovirus take time and require sophisticated laboratory equipment.
So when Tucson's water utility approached her for help improving on the status quo, Reynolds she thought she knew how to find a cheaper, and faster approach.
She asked her University of Arizona colleague Jeong-Yeol Yoon, a biomedical engineer, if he could build an inexpensive norovirus detector, and he said yes.
Yoon's lab specializes in building small, handheld devices for testing water quality and food safety. Many of these devices use a cell phone camera attached to a microscope.
"You can buy the microscope attachment to a smartphone very easily," Yoon says. "In the past the magnification is about 60x and 100x. Nowadays you can get 200x, 400x and 600x and they are still under $100 dollars."
The norovirus test he's developed also uses paper-based microfluidic chips. These are inexpensive wafers that draw water samples onto them, so there's no need for external pumps.
Even with available magnification, the viruses are too small to see. So Yoon mixes a water sample with tiny fluorescent polystyrene beads coated with antibodies to the norovirus. If the virus is in the water sample on the paper chip, the beads will clump around the virus, making it possible for the cell phone camera to detect them.
Yoon says the device works rapidly.
"From sample to answer...five minutes," he says.
Yoon presented details about his invention on August 27 at the American Chemical Society National Meeting in San Diego. A paper describing preliminary results with the device is published in ACS Omega.
Even though most norovirus infections are acquired from eating contaminated food, having a sensitive enough test to reliably detect the virus in water samples "would be useful," says Rachel Noble, Mary and Watts Hill Jr. Distinguished Professor in the Department of Environmental Sciences at the University of North Carolina.
In the wake of hurricanes and other storms, flooding can cause sewage systems to overflow, potentially mixing with water intended for drinking. Municipal water system managers would breathe easier if they could be certain they didn't have to worry at all about norovirus contamination.
She says she and other researchers have worked on similar projects to develop a speedy test for norovirus. Yoon's device shows promise, but "a lot of these ideas work in the lab," says Noble. Unfortunately, once they're tested in the real world, they tend not to work so well. Especially unwelcome are false negatives, i.e declaring a water virus free when it really isn't.
"The may only be a few virus particles in a water system," says Noble. But those few particles could still cause illness, and might be missed in a test sample.
Yoon's device still faces rigorous testing to make sure it can accurately identify contaminated samples. For now, much of the testing is trying to be certain that people can operate the test reliably.
"Volunteers from my laboratory, some students and other staff around the lab are just testing the smartphone tool just to see how user friendly it is," Arizona's Reynolds says. These are people with "with very little knowledge about infectious disease or about viruses or even water sampling," she adds.
Reynolds says initial results are encouraging.
"We'll be transitioning the field trials to Tucson water employees in the fall," she says. That should help determine just how reliable the new device is.
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