Researchers have created a version of CRISPR-Cas that can be used to diagnose infections, such as Zika and dengue, with a high level of sensitivity. The advancement could help facilitate rapid detection and diagnosis of many other pathogens, too. While some methods exist for detecting genetic sequences, they have trade-offs among sensitivity, specificity, simplicity, cost, and speed. In the search for a more effective method, Feng Zhang, Jonathan S. Gootenberg and colleagues turned to a CRISPR-Cas system that targets RNA. Binding the target RNA activates this particular Cas enzyme to promiscuously cleave nearby RNA. They exploited this by including a reporter RNA that releases a fluorescent signal when it is cleaved, and used a technique, called recombinase polymerase amplification, to further boost sensitivity. This combination resulted in a system, which the team dubbed SHERLOCK (Specific High Sensitivity Enzymatic Reporter UnLOCKing), that could detect rather low titers of Zika virus in serum, urine, and saliva. SHERLOCK can also be used to measure viral load, the authors show. Next, they found that the technique was effective at identifying various bacterial strains, even differentiating between strains of bacterial pneumonia with different resistance mutations. Lastly, the authors show that SHERLOCK can be used to detect different cancer mutations. A SHERLOCK test can be redesigned and synthesized in a matter of days for as low as $0.61/test, the authors say, noting that the high sensitivity of the system opens new avenues for rapid, robust and sensitive detection of biological molecules.