Pasteur, Henle, Koch, Virchow, and soon battalions of bacteriologists and pathologists, firmly established the fact that micro-organisms caused many diseases – the germ theory was fact, not theory. But many germ diseases require much more than germs before they can do their worst damage. Tuberculosis is caused by the tubercle bacillus acting in conjunction with poverty, ignorance, overcrowding, poor nutrition, adverse social and economic circumstances and other enabling and predisposing factors.

The diarrheal diseases including cholera are caused by various micro-organisms, but these get into the gut when ingested with contaminated water or food, that is, they are really caused by poor sanitary and hygienic practices.