While medical and hygienic developments have driven down the
mortality rates of infectious diseases, pathogenic microorganisms
are still a major factor in everyday clinical practice. They are
still the most frequent cause of death in Third World countries.
New and incurable infectious diseases are a worldwide problem. It
is inescapable, therefore, that modern medicine must redouble its
efforts to understand the relationship between microorganisms and
humans and continue to lead the search for new therapies.