ABSTRACT
Ask a group of people in a high-income country today what disease they most fear, and they are likely to say cancer, dementia or perhaps stroke. They are unlikely to name an infection. This is a very modern phenomenon. Down the centuries, public health interventions have improved human health in many ways, but two stand out: sanitation and vaccination. Knowledge and skills in observing the passage of infections through populations, and ways to control their spread, have been a feature of public health practice since late Victorian times. The term epidemic is much less commonly used than it used to be. The pattern of disease it describes could usually just as easily be called an outbreak. Bacteria are single, living cells, able to replicate themselves. Many are beneficial and essential to life. A reservoir for a communicable disease is any person, animal, etc, multiplies and relies upon for survival, and from where it can infect a person, animal vector.
