From the WellcomeTrust: “In the mid-19th century, John Snow mapped cases of cholera in Soho, London, and traced the source of the outbreak to a contaminated water pump. Now, in a 21st-century equivalent, scientists funded by the Wellcome Trust working in Kathmandu, Nepal, have combined the latest in gene sequencing technology and global positioning system (GPS) case localisation to map the spread of typhoid and trace its source.
To capture the information, health workers would visit a patient’s home and use GPS to capture the exact location. They would also take a blood sample from the hospitalised patient to isolate the organism and to allow analysis of the typhoid strain’s genotype – its genetic make-up. This genotyping used sequencing technology able to identify single changes in the ‘letters’ of DNA – the A, C, T and Gs that make up the code.”