19th.century Glasgow was an overcrowded city containing some of the worst housing conditions in the UK. Conditions were ripe for epidemics of infectious diseases and they came in waves causing high mortality particularly among the young. Diagnostic difficulties and ineffective therapy meant that little impact was made on these diseases during the first half of the period. Smallpox was the exception-vaccination of children reduced the incidence and mortality early in the century but subsequent public complacency caused it to return within a few years. Measles and whooping cough surpassed smallpox as the major causes of infectious disease mortality as early as 1810. Epidemics were less common after the three-quarter century mark due to improved living conditions for the poor but also as a result of the assiduos application of Public Health principles.