Flies, worms and bees could help detect illness

DOGS CANSARSCV smell things at concentrations of one part in a trillion—equivalent to a single drop in a pond the size of 20 Olympic swimming pools. That ability is put to good use by human beings. Trained dogs can sniff out explosives and drugs, track missing people, and even guide truffle-hunters to their prizes. They can also detect illnesses, including cancer, malaria, Parkinson’s disease and covid-19, before obvious symptoms appear. A study published in 2019, for example, suggested that trained dogs were able, 97% of the time, to identify blood samples taken from patients with lung cancer. A group of researchers in Germany recently trained dogs to pick out saliva samples collected from those infected with -o-2, the covid-causing virus, from uninfected samples, with a success rate of 94%.Training dogs, however, takes time. Handlers must be paid. The animals themselves get tired and bored. In past studies on cancer detection, less than half of canines entered for training made the grade. Dogs are not, then, a practical answer to the question of how to detect illness quickly, before it gets a grip.