A new technique for detecting viruses works by listening to them
TREATING viral diseases is notoriously hard. One reason is that
for many such diseases, the amount of virus in a patient's
bloodstream (known as the viral load) has to be monitored
carefully in order to work out the appropriate drug dose. At the
moment this is often done by quantitative PCR, which uses an
enzyme called polymerase to “amplify” part of a virus's genetic
material by repeated duplication, until it is chemically
detectable. But quantitative PCR is time-consuming; and in viral
diseases time is often of the essence. Now a technique described
in Nature Biotechnology by Matthew Cooper and his colleagues at
Cambridge University may provide that essential time. Instead of
detecting viruses chemically, Dr Cooper listens for them. To do
this, he and his colleagues use an apparatus called a quartz
crystal microbalance. The balance is a disc made of a polished
quartz crystal, with two electrodes attached to it. Sending an
electric current of t