Paper discs that detect Ebola are being developed for use as a rapid, cheap, simple method to identify infected people.

According to Harvard‘s Wyss Institute‘s Jim Collins, the technology prints sequences of DNA on paper, and then the paper is freeze-dried and stored at room temperature. The DNA is reactivated by adding water. Once active, it enables the paper to change color if a chosen target – such as a segment of Ebola viral RNA – is present in the water.

The target fragment binds to a gene switch in the DNA, which triggers the production of a colorful substance. The paper changes color to indicates which of the target pathogens has been detected.

Wyss researcher Keith Pardee improved the test by inserting tailor-made gene switches that prevent color change unless a very specific target molecule is present. The synthetic “toehold” switches enabled the paper to simultaneously test for 24 distinct regions of viral RNA – many more than would have been possible using only naturally occurring DNA sequences. This distinguished between a synthetic version of the Zaire strain of Ebola – the one responsible for the west African epidemic – and a synthetic version of another known as the Sudan strain.

The test identified the strains within 30 minutes.