Two of the worlds biggest threats may someday be reduced by wires thousands of times thinner than a hair but capable of detecting a single virus. The specter of worldwide viral epidemics is always with us, so detecting them quickly offers the possibility of saving thousands of lives. The pathogens also can be stealthy biological weapons, making their positive detection a vital national defense requirement.
— Read on news.harvard.edu/gazette/story/2004/10/sensor-detects-identifies-single-viruses/

H/T Godfree Roberts

Charles Lieber was working on detecting mass viruses, especially biological weapons.