Explaining why he devoted three chapters of his autobiography to what he labelled ‘The Black Plague’ – the pneumonic plague epidemic that struck Johannesburg in March–April 1904, killing eight-two people – Mahatma Gandhi wrote, ‘the whole incident, apart from its pathos is of such absorbing interest and, for me, of such religious value’ that it merited that amount of attention. But, as historians of epidemics, ever since Thucydides, have recognized, epidemics are of interest for reasons beyond these, in particular for the immediate and long-term marks they leave on affected societies, as well as the light they shed on prevailing social attitudes which can sharpen and become more manifest in response to the threat to life posed by a terrifying, runaway outbreak of a lethal disease. As one historian of the Black Death memorably put it, an epidemic is a ‘stimulus … which exposed the nerve system of … society’.

In this way, attitudes and outlooks which otherwise might not be apparent can be seen – the Romans might have said ‘In pestilentia veritas’ (‘there is truth in a plague’). In the case of a high-profile individual like Gandhi, views of his surfaced under the duress of the epidemic which show a different side to him, one not wholly in keeping with the popular image of the caste-blind, class-blind, colour-blind, unprejudiced, egalitarian, universalist mahatma cherished by his acolytes and many of his biographers.