Microbial factors in disease emergence illustrated by streptococcal toxic shock syndrome.

Abstract

Factors contributing to the emergence of infectious diseases will be reviewed briefly to provide a background for a discussion of the sharp decline in the occurrence of group A streptococcal disease that began early in this century before the use of antibiotics, and the emergence of streptococcal toxic shock syndrome (STSS) in the last decade. The strains of group A streptococci that cause STSS have been dubbed ‘the flesh-eating bacteria’ by the media, and are the focus of this paper. Be aware that none of the factors contributing to disease emergence operates in isolation; there is endless overlap and interplay. ‘Microbial traffic’ introduces microbes to new domains where they find people and animals unprotected by prior experience. They hitchhike along with all of us in travel and commerce, accompanying the one million air passengers that fly each day. How many alien microbes did they bring with them right into the conference hall when they arrived in Kyoto with participants of this symposium? But people are not the only expediters of international movement of microbes. Pathogens can be flown in on fresh foods rushed to our dinner tables. Influenza viruses migrate with aquatic birds that carry viral genes to new venues to combine through genetic reassortment with resident flu viruses. As in the past, new flu viruses can emerge from this union that possess unusual virulence to spread around the world. Thus, microbial traffic facilitates the emergence of infectious diseases from microbes that already exist and microbes that emerge from genetic changes and evolutionary selection [1–3]. Disease vectors travel also to new environments. Ocean transport ships provide passage for rodent stowaways and insects that breed in recycled vehicle tyres, carrying them to new domains where they find new ecological niches. Insect vectors especially are on the loose again, …