(Question 17) Discuss the following statement:

(Question 17) Discuss the following statement:

“Infectious agents will emerge so long as there are microorganisms. Humans help the evolutionary process sometimes unwittingly and sometimes by arrogance or ignorance” (Stanley Falkow, 1998).


Answered by Nicole Hendricks


Stanley Falkow is the former chair of the Department of Medical Microbiology at Stanford University School of Medicine and currently Professor of Microbiology and Immunology at Stanford University- his writing reflects a great understanding of infectious diseases and he often speaks liberally on the ‘misunderstood’ microbe.

By definition a pathogen is an organism capable of causing disease, not with the intention to do so but as a by-product of its mechanisms of invasion and establishing itself within any given host. Therefore infectious agents do not intend to harm their human host but rather are simply utilising strategies and opportunities developed in order to reproduce. For example, organisms such as shigella, possess plasmids that exist apart from the bacterial chromosome and they can carry specialized information for survival. Under selective pressure from antibiotics, one species of bacteria can pass its plasmids to another unidirectionally rather than by mating, thereby preserving its own survival genes.

Falkow states that from the beginning of recorded history infectious disease has been the leading cause of morbidity and mortality; and this is still true today. For developing countries where poverty, unsanitary living conditions, forced proximity and malnutrition are often part of daily life- people will not have the luxury of succumbing to ‘age’ related diseases but death will more likely be a product of an infectious disease. For us as a developed nation; we may have the resources to develop medicines and generally do not suffer the same effects of poverty. We may have improved our life expectancy and we may be facing different microbes then we had to 100 years ago (eg vaccination of polio but resurgence of HIV), but the same number of people are die of infectious diseases globally as they did 40 years ago. We are under the false perception that we have mastery over the microbe. They always have been and always will be the true survivors.

Infectious disease are still believed to be the leading cause of death worldwide for four primary reasons: 1) our populations have/are large enough to support parasites many of which have adapted to utilise a human host 2) poverty for the aforementioned reasons increase susceptibility to disease 3) civil unrest, war & famine have led to the breakdown of infrastructure and increased incidence in infection 4) the domestication of animals and increased proximity to their environments has promoted the emergence of new diseases ie. Lyme disease.


Therefore, Falkow suggests we refer to emerging diseases as ‘disease of human progress’, that as consequence of our interaction and changes in behaviour we have coerced as well as provided opportunity of microbes to cause human infection/disease. Some diseases such as typhoid bacillus and gonococcus have developed specifically as human pathogens they’ve evolved the genetic ability to breach cellular and anatomic barriers that ordinarily restrict other microorganisms and in doing so have access to new nutrients and a less competitive environement. Others such as Legionella pneumophila have been introduced into our environment and have found a new niche in the avleolus macrophage instead of in its usual host Acanthamoeba or Hartmanella.