Researchers from the University of Pennsylvania have developed a cheap and quick test for the Zika virus. The patient needs to provide only a saliva test which turns blue in the presence of the virus — and it only costs $2.
Rapid, accurate diagnosis of Zika is vital, especially for pregnant women. While the disease is not typically life-threatening for adults, it can cause microcephaly (underdevelopment of the brain and head) and other devastating birth defects. It is estimated that 1.5 million people have been infected by Zika in Brazil, with over 3,500 cases of microcephaly reported between October 2015 and January 2016.
Having a test which could quickly identify the disease is no easy feat. The genetic material from the Zika itself is considered the golden standard for disease detection because other, indirect methods (like detecting Zika-fighting antibodies) can create false positives from people who are infected but haven’t yet produced enough antibodies, or false positives from people who have antibodies for a different disease that is similar enough to trigger the test. But genetic tests are generally time-consuming and require specific lab equipment (which also costs a lot).
“The CDC has approved, on an emergency basis, only these kinds of laboratory-based molecular tests for the Zika virus,” said Research Assistant Professor Changchun Liu. “Generally, lateral flow tests, which directly change the color of a test strip based on the presence of Zika antibodies, suffer from low sensitivity. And since antibodies to the Zika virus cross-react with other similar viruses prevalent in Zika-endemic areas, lateral flow tests for Zika also suffer from low specificity.”
This is where this research steps in. They developed a procedure which provides a genetic test without requiring the very specific lab processes. Their solution involves a thermos bottle, a self-contained heating element that uses a chemical reaction from portable military rations and a wax-like material that absorbs excess heat by melting. A 3-D printed lid fits on top of the thermos and holds all of the test’s components in place.
“In parallel,” Liu said, “we engineered a low-cost, point-of-care system that consists of a diagnostic cassette and a processor. The cassette isolates, concentrates and purifies nucleic acids and carries out enzymatic amplification. The test results are indicated by the change in the color of a dye, which can be inspected visually.”
All you need to do is insert the saliva into the cartridge and wait for 40 minutes. So far, initial tests have proven to be very promising and researchers want to test them at a much greater scale.
“Our work represents a proof of concept at this stage,” said Professor Haim Bau of the Department of Mechanical Engineering and Applied Mechanics in Penn’s School of Engineering and Applied Science. “Before the assay can be adapted for medical use, we must experiment with patients’ samples and make assure that our assay and system match the performance of the gold standard and operate reproducibly and reliably. We are fortunate to have dedicated colleagues in endemic regions ready to assist us in this task.”
As it stands at the moment, the virus has created an epidemic throughout South America, with no end in sight. The outbreak began in April 2015 in Brazil, and has spread to other countries in South America, Central America, Mexico, and the Caribbean. In January 2016, the WHO said the virus was likely to spread throughout most of the Americas by the end of the year.
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