Bazalgette was appointed assistant surveyor to the Commission in 1849, taking over as Engineer in 1852, after his predecessor died of "harassing fatigues and anxieties." Soon after, another cholera epidemic struck, in 1853, killing 10,738. Medical opinion at the time held that cholera was caused by foul air: a so-called "miasma". Physician Dr John Snow had earlier advanced a different explanation, which is now known to be correct: cholera was spread by contaminated water. His view was not then generally accepted.