Infectious disease has been a leading cause of death in humans since the first recorded tabulations. Major pandemics of bubonic and pneumonic plague, cholera, smallpox, measles, tuberculosis, syphilis, gonorrhea and influenza have devastated the human population. In the immediately post natal period, the placental site is a large open wound – easily invaded by ascending bacteria. That puerperal women were at risk of a fever that could be fatal was common knowledge. Puerperal sepsis (childbed fever) was known since 1500 BC but it was the Hungarian obstetrician Ignaz Semmelwies who discovered its cause and first took preventive measures against the spread of this serious infection.