After the 1854 outbreak, a number of major infrastructure changes were put in place to clean up the water supply for the city.

The most formidable of them all was the creation of the London sewers and really one of the most extraordinary engineering achievements of the 19th century.

A massive project actually completed in a remarkably short amount of time, really about five or six years.

In 1866, an outbreak appeared in the East End of London.

John Snow had died about seven or eight years before that, but William Farr immediately treated it as a problem of contamination from drinking water.

He began investigating it.

And in a way, you can see that as the moment where the modern system of public health, of collaboration across disciplines from state institutions to infrastructure, to individual medical practitioners, reporting data, all of those things, converged to stop this outbreak of cholera in 1866.

And that was the last time the cholera has appeared in London ever since.