Half the world's population is at risk of Dengue virus infection – it infects 50-100 million people per year, approximately half a million of these require hospitalization and 2.5% (most of which are children) will die. It is one of the most dangerous viruses in the world with no vaccine, and it does not respond to antiviral therapy. The main method of controlling infection remains destruction of the standing water where the mosquitoes, which transmit the virus to people, breed.
It is consequently vitally important to have a way of determining if mosquitoes are carrying Dengue virus, which can be used on site and that does not require specialist equipment.
Researchers from the University of Notre Dame, USA, used a DNAzyme linked to gold nanoparticles which recognises a short sequence of the viral RNA genome common to all four types of Dengue. Once bound, adding magnesium and heating to 37C causes the DNAZyme to cut the RNA leaving the gold nanoparticles free to clump together. This aggregation can be easily seen as a red to clear/colourless colour change.
The components of this test are stable at temperatures above 30C which means that they are easy to store and transport and the assay is able to detect as little as 10 viruses in each sample containing 10-20 mosquitoes.
The ultimate goal is to detect virus infection in just a single infected mosquito or cell. Dr James Carter, the lead author of this study explained, "Full development of our novel DDZ-AuNP detection method will provide a practical, rapid, and low cost alternative for the detection of DENV in mosquito cells and tissues, and possibly infected patient serum, in a matter of minutes with little to no specialized training required."