Portable Test Quickly Detects Zika Virus in Saliva for $2

Disposable cassette identifies Zika genetic sequence within 40 minutes

Anxiety over the Zika virus is growing as the Olympic Games in Rio de Janeiro approach. To better diagnose and track the disease, scientists at the University of Pennsylvania have developed a $2 test that can accurately detect low levels of the virus in saliva. Their work was reported online in Analytical Chemistry, a journal of the American Chemical Society.

The World Health Organization (WHO) recently announced that there was no need to postpone or move the Olympics because of Zika’s presence, but concern over the virus’ spread and its link to serious birth defects is far from allayed. Public health experts debate whether WHO made the right call. While the discussion continues, scientists are working on new tools to help manage the outbreak.

Current gold-standard tests to detect the Zika virus require expensive laboratory equipment and trained personnel. Low-cost diagnostic methods have been reported, but they can’t detect low levels of the disease or distinguish between Zika and similar viruses, such as dengue.

The scientists at Penn wanted to design a rapid, low-cost, and more-reliable point-of-care detection test. Their efforts resulted in a so-called reverse-transcription loop-mediated, isothermal amplification (RT-LAMP) assay. The assay is implemented in an easy-to-use, inexpensive, point-of-care disposable cassette that carries out all of the unit operations from sample introduction to detection. For thermal control of the cassette, the scientists used a chemically heated cup without a need for electrical power.

To ensure that their system would be highly selective for Zika without confusing it with similar viruses, the researchers looked for and found a stretch of genetic code that is nearly identical for 19 strains of the Zika virus infecting people in the Americas but not for other pathogens. Then, with materials costing $2 per test, they developed a diagnostic system that requires only the addition of water to operate.

If the Zika-specific genetic sequence is in a saliva sample, a leuco crystal violet (LCV) dye within the system will turn blue within 40 minutes. The test even works if low levels of the sequence are present.

The system is particularly suitable for resource-poor settings, where centralized laboratory facilities, funds, and trained personnel are in short supply, and for use in doctors’ offices, clinics, and at home, according to the researchers.

Sources: American Chemical Society; June 29, 2016; and Analytical Chemistry; June 16, 2016.