Biomedical Engineering Reference
In-Depth Information
Appendix III
Organisms Causing Infectious
Disease in Humans
“The botanist is he who can affix similar names to similar vegetables, and different
names to different ones, so as to be intelligible to every one.”
Carolus Linnaeus
A few hundred organisms account for virtually all of the infectious dis-
eases that occur in humans, and all of these organisms are listed in the text
of the topic. In addition, there are many “case report” pathogens that account
for just a few known instances of human disease. Some of these infections
are isolated within a small and relatively uninhabited geographic area. Some
are veterinary diseases that do not ordinarily infect humans, but can cross
over to produce self-limited human disease when the infective load is high
(e.g., when a handler is exposed to a large number of organisms). Some are
passed by eating exotic and undercooked food. Many of the ultra-rare infec-
tious diseases in humans are well-known to veterinary pathologists, who
routinely see and treat these infections in animals.
Some of these infections are opportunistic and occur in a highly select sub-
set of vulnerable individuals (immunosuppressed, diabetic, renal-compromised,
neonatal, elderly, malnourished, etc.). For the most part, diseases that arise
in immune-compromised individuals are either commensals (typically non-
pathogenic organisms that live in our bodies), or sub-clinical environmental
pathogens (organisms encountered in the environment that do not cause overt
disease in the majority of healthy individuals).
The Appendix contains about 1400 organisms that are pathogenic in
humans, collected from many different literature sources [144,145]. Has
every infectious organism been listed in the appendix? Not at all. New
pathogenic agents are constantly arising for a variety of reasons: improved
diagnostic methods, demonstrating specific organisms that can cause a single
disease or lesion; known organisms, previously thought to be benign, that are
found to cause disease in immune-deficient individuals; very rare organisms,
located in an isolated geographic location, that had previously escaped atten-
tion; newly described subspecies of previously known infectious species;
previously non-pathogenic organisms that acquire a virulence factor; viral
