Since population was increasing in Great Britain at the same time that landowners were enclosing common village lands, people from the countryside flocked to the towns and the new factories to get work.
Infectious disease was an expected, almost everyday feature of nineteenth-century life. Smallpox, typhus, typhoid, dysentery, diphtheria, scarlet fever, tuberculosis and cholera were among the many illnesses that made cities - the industrial cities in particular - unhealthy places to live. Overcrowding, malnutrition, and poor hygiene and sanitation assisted in the cultivation and spread of disease.
Any disease that is able to spread among the community may for normal intents be called infectious. In its accepted sense, an infectious disease is one which travels through the general environment as it passes from one person to another.