Now, a device clipped with smartphone can help detect Zika virus
Zika virus is primarily transmitted through Aedes aegypti mosquitoes. Although the disease is largely asymptomatic or results in mild symptoms in adults, it causes developmental disorders in newborn babies if their mothers are infected during early pregnancy.
"Mosquito-borne viruses cause serious diseases, but they have similar symptoms. If you have Zika, malaria, dengue, or chikungunya, you just might show up to the doctor with a fever and they won't know why," said Brian Cunningham, a faculty at University of Illinois Urbana-Champaign.
Stressing the need to identify the virus as Zika causes developmental disorders in new-borns, he adds, "But it's important to know whether it's Zika, especially if the patient is a pregnant woman, because the consequences to a developing foetus are really severe."
Zika virus infections are currently detected through polymerase chain reaction (PCR) tests performed in laboratory, which can amplify the genetic material of the virus, allowing scientists to detect it. Although the laboratory-based methods are rapid, simple, accurate, and sensitive, it often require trained personnel and involve complex procedures.
Here, the researchers used Loop-Mediated Isothermal Amplification to detect the virus in the blood samples using an approach suitable for remote testing. While PCR requires 20-40 repeated temperature shifts to amplify the genetic material, LAMP only requires one temperature - 65°C - making it easier to control.
PCR tests are very sensitive to the presence of contaminants, especially the other components in a blood sample. As a result, the sample is first purified before it can be used. Whereas, LAMP does not require any such purification step.
A cartridge that contains reagents required to detect the virus is inserted into the instrument to perform the test, while the instrument is clipped onto a smartphone. Once the patient adds a drop of blood, one set of chemicals break open the viruses and the blood cells within five minutes. A heater below the cartridge heats it up to 65 °C.
A second set of chemicals then amplifies the viral genetic material, and the liquid inside the cartridge fluoresces bright green if the blood sample contains the Zika virus. The entire process takes 25 minutes.
"We've designed a clip-on device so that the smartphone's rear camera is looking at the cartridge while the amplification occurs. When there's a positive reaction, you see little green blooms of fluorescence that eventually fill up the entire cartridge with green light," Cunningham said.
The researchers are now developing similar devices to simultaneously detect other mosquito-borne viruses and are working on making the devices even smaller.