- Detection of noroviruses from common environmental matrices (water and food) involves a complicated concentration of viruses and / or amplification of the genetic material, making detection approaches for field applications unworkable.
- A smartphone-based fluorescence microscope developed by us and an image processing algorithm isolated only the particles that were aggregated by antibody-antigen binding.
- This resulted in an extremely low detection limit for noroviruses of only 1 genome copy / μl in deionized water and 10 genome copies / μl in treated wastewater.
A sensitive new device can detect tiny amounts of norovirus in the water, reports Phys.org.
Norovirus – Infamous cruise virus
Norovirus, notorious for cruise ship breakouts, can really ruin a vacation, causing severe vomiting, diarrhea, and stomach pain.
However, the highly infectious virus can also occur near home. In urban water systems, schools and restaurants, outbreaks are caused by water and food.
Scientists have come up with a sensitive, portable device that can even detect very minute norovirus particles in water.
Researchers will present their findings at the National Meeting & Exposition of the American Chemical Society (ACS) in the fall of 2019.
PCR for virus detection
“There is only a very small number of norovirus particles required to trigger an infection in humans sensitive detection method,” says Jeong-Yeol Yoon, Ph.D., who led the team.
“In addition, scientists are unable to grow noroviruses in the lab, and the available antibodies to the pathogen are not very strong.”
The detection of very small amounts of Norovirus in water or food samples therefore usually requires a multi-hour PCR (Polymerase Chain Reaction) method, which must be performed by trained personnel in a laboratory.
Smartphone-based device
Yoon and his colleagues from the University of Arizona developed a smartphone-based device that can detect low levels of norovirus by measuring the light scattering of virus-bound polystyrene beads in a microfluidic paper chip.
“Although our detection limit was really low, the problem was that Norovirus could be infectious in even lower concentrations,” says Yoon.
“When we spoke at conferences about this work, we received feedback that we needed an even simpler method to detect much lower levels of virus.”
Fluorescence rather than light scatter
So the team went back to the lab and developed a new approach that uses fluorescence, rather than light scattering, to detect norovirus.
The researchers converted an ordinary smartphone into a fluorescence microscope by attaching a commercially available light microscope accessory, a separate light source and two band-pass filters.
To a channel of their paper microfluidic chip, they added a water sample containing norovirus. Then, the researchers added a suspension of fluorescent beads with antibodies against norovirus attached to them.
The capillary action of the paper caused the two liquids to flow and mix. Each individual norovirus particle bound to multiple fluorescent beads via their attached antibodies, causing the beads to aggregate and produce a much larger size of fluorescent image.
Recently, Yoon and colleagues have made the system more compact and handy by enclosing the fluorescence microscope, the light source, and the optical filters in the housing with a 3-D printed envelope.
Cloud computing app
They also developed a cloud computing app to analyze the big images and send the results back to the smartphone. In addition, they have found a way to focus samples in the paper chip to analyze much larger sample volumes.
The device was able to detect minute amounts of norovirus in both purified and recycled wastewater, which is heavily contaminated. Tap water, on the other hand, was error-prone. “We believe the chlorine in tap water affects the test,” says Yoon.
“We do not think it will be a problem to treat the water before carrying out our method to remove chlorine.” Yoon estimates that community water system workers could use the device and app to check the water supply to noroviruses.
To test the use of the assay in the field, the team collaborates with Kelly Reynolds, Ph.D., at the same institution and with Tucson Water.
Diagnosing Noroviral infections
Now, Yoon and colleagues are working to use their smartphone device to diagnose norovirus infections in patients at an earlier stage than is currently possible. To do this, they plan to analyze stool samples.
“If the Norovirus reaches detectable levels using other methods, the person is already seriously ill,” says Yoon. “But if we recognize the virus earlier, they can be treated medically sooner.”
Early detection can also help curb the spread of disease in isolated, overcrowded situations such as cruise ships, where the distinction between a normal stomach upset and a norovirus infection can guide quarantine efforts or speed up the transportation of a passenger to port for treatment.
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Source: Phys.org
