Cholera is an acute illness caused by infection of the intestine with the bacterium 'vibrio cholerae'. In severe cases the symptoms are profuse watery diahorrea, vomiting, and leg cramps. In these cases, rapid loss of body fluids leads to dehydration and shock and in the mid-19th century, which lacked an effective treatment, death could occur within hours.
These statistics show the severity of the infection in Victorian Wales, since just under half the people who were infected died of it - 1,520 dead out of 3,612 cases in just a few months. (The first case recorded here was on 25 May 1849 in Merthyr, so all of these cases occurred between 25 May and 22 September.)

People usually catch the disease through drinking contaminated water, and areas without clean drinking water are most at risk.