Norovirus kills 200,000 annually, but now armed with just a smartphone scientists can detect tiny amounts of the pathogen
A research team has developed a simple, portable, and inexpensive method to detect extremely low levels of norovirus in water, by using a smartphone. Norovirus is a highly contagious disease that kills 200,000 globally every year and just 10 norovirus particles can cause illness in people. Current methods to detect the virus in small quantities require lab settings, which are time-consuming and very expensive. The new finding is expected to tackle these difficulties.
According to researchers from the University of Arizona, one need not be a scientist or an engineer to run the smartphone-based device. Analysis will be done automatically by the smartphone app. All one needs to do is load a sample of water on a chip.
Infected people shed billions of virus particles. Made infamous by outbreaks on cruise ships, norovirus can cause severe vomiting, diarrhea and stomach pain. But the highly infectious virus can also strike closer to home, with water- and food-borne outbreaks occurring in municipal water systems, schools, and restaurants. The research team says that municipal water systems staff could easily use the device and app to check for norovirus in the water supply.
“Advances in rapid monitoring of human viruses in water are essential for protecting public health. This rapid, low-cost water quality monitoring technology could be a transformational tool for reducing both local and global disease burdens,” says Kelly A. Reynolds, chair of the Department of Community, Environment and Policy in Mel and Enid Zuckerman College of Public Health, The University of Arizona.
The findings have been published in ACS Omega, the official journal of the American Chemical Society, and the analysis was also presented at the ACS Fall 2019 National Meeting & Exposition in San Diego.
Disease burden of norovirus is high
According to the Centers for Disease Control and Prevention (CDC), norovirus illness is a problem in both low- and high-income countries. From a public health perspective, experts say, numbers show that young children experience the highest incidence of disease and severe outcomes are most common among young children and the elderly.
About one in every five cases of acute gastroenteritis (inflammation of the stomach or intestines) that leads to diarrhea and vomiting is caused by norovirus. Norovirus causes 685 million cases of acute gastroenteritis, making it the most common cause of acute gastroenteritis worldwide. Further, CDC estimates state that about 200 million cases are among children under 5. Among the estimated 200,000 deaths that are caused by norovirus every year, 70,000 or more deaths are among children, mostly in developing countries. Further, every year norovirus is estimated to cost $60 billion worldwide due to healthcare costs and lost productivity.
Current methods are expensive and time-consuming
Devices to detect norovirus in small quantities do exist, but they typically require a laboratory setting with an array of microscopes, lasers, and spectrometers that can cost thousands of dollars. To detect norovirus in the field, such as in municipal water wells, the team decided to use much simpler materials: paper, in the form of microfluidic chips, and a smartphone.
According to the researchers, since it only takes a very small number of norovirus particles to cause an infection in humans, their study focused on creating a very sensitive detection method. “Scientists are not able to culture norovirus in the lab, and available antibodies to the pathogen aren’t very strong. As a result, detecting very small amounts of norovirus in water or food samples typically involves a polymerase chain reaction (PCR)-based method, which takes several hours and must be conducted in a lab by trained personnel,” says Jeong-Yeol Yoon, from the Department of Biomedical Engineering, The University of Arizona.
How does the new device work?
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.
The process starts with adding potentially contaminated water to one end of a paper microfluidic chip. To the other end, a tester adds tiny, fluorescent polystyrene beads. Each bead is attached to an antibody against norovirus. If norovirus is present, several of the antibodies attach to each virus particle, creating a little clump of fluorescent beads. The team snapped photos of the chip with their smartphone-based fluorescence microscope, and an app calculated norovirus concentrations from the pixel count of the images.
“These clumps of beads are large enough for a smartphone microscope to detect and photograph. A smartphone app (also created by the researchers) counts the number of illuminated pixels in the image to identify the number of aggregated beads, and subsequently, the number of norovirus particles in the sample. That is another advantage of the paper chip: Through capillary action, the groups of beads spread out along the paper, making them easier to count,” the findings state.
It adds, “The lowest detection limit corresponded to about 5 or 6 norovirus particles per sample, so it’s very close to the single-virus level. Because as few as 10 virus particles can cause illness in people, the new method is sensitive enough for practical applications.”
The most expensive component of the whole device - the smartphone microscope - costs less than $50. The device could detect minuscule amounts of norovirus in both purified water and reclaimed wastewater, which is very dirty. Tap water, on the other hand, was prone to error. “We do not think it will be a problem to treat the water to remove chlorine before performing our method,” says Yoon.
The researchers are now expanding the scope of their research and are working on using their smartphone-based device for diagnosing norovirus infections in patients at an earlier stage than is currently possible. Early detection, says the team, might also help curb the spread of disease in isolated, crowded situations like cruise ships, where distinguishing between a run-of-the-mill upset stomach and a norovirus infection could guide quarantine efforts or expedite getting a passenger to a port for treatment. In the future, the team also hopes to expand their smartphone monitoring platform to detect other hazards, such as potentially cancer-causing chemicals.