Contact tracing programme will get virus under control

Dr Keith Souter takes a look at the history of epidemiology as the UK prepares to launch its ‘test, track, trace’ programme to tackle the coronavirus pandemic

THE SCIENCE of epidemiology has come to everyone’s attention during the Covid-19 pandemic.

The government’s target of 100,000 tests per day has been reached and the next step is to begin its contact tracing programme, which experts say is the UK’s best chance of keeping the coronavirus under control and easing the lockdown.

This ‘test, track and trace’ programme is going to begin soon and will include the use of a downloadable smartphone app that will alert if one has been in contact with a confirmed case of Covid-19. It is based on the method used by the father of epidemiology in the 19th century. Dr John Snow was a doctor living and working near Soho in London in the early 19th century. Back then London was a highly unsanitary place to live. Infectious diseases were rife.

The so-called enteric fevers affected huge numbers in epidemics, leading to many theories as to how they were caused. The most popular was the ‘miasma theory’ which postulated that the fevers were caused by foul dampness arising from decaying organic matter. In the mid-19th century people used town wells and communal pumps to get the water they used for drinking, cooking and washing. Septic systems were primitive and most homes and businesses dumped untreated sewage and animal waste directly into the

Thames River or into open pits or cesspools.

In 1854 Soho was hit by one of the periodic cholera epidemics. Dr Snow charted on a map each and every case that resulted in a death. He found that within 250 yards of the spot where Cambridge Street joins Broad Street there were 500 fatal attacks of cholera in ten days. Further investigation showed that the majority of cases had consumed water from the Broad Street pump. He concluded that contaminated water was causing the epidemic.

After presenting his findings to officials, the handle of the Broad Street pump was removed and gradually the number of cases dwindled and stopped.

By contact tracking and tracing Dr Snow had demonstrated the mode of cholera spread and halted the epidemic. We have to thank him for his method upon which this smart use of technology is based.