A much used term nowadays, "contagion" or in adjective form, "contagious," is derived from Latin contāgiō (touching, contact, contagion) related to contingō (touch closely). In its original meaning, the term referred solely to a disease transmissible by direct physical contact. Nowadays, its meaning has been broadened to include all communicable or infectious diseases. As Wikipedia says: "Often the word can only be understood in context, where it is used to emphasize very infectious, easily transmitted, or especially severe communicable disease." Sure, because of its scary connotation, it made it into the title of a mighty frightening movie.
aerosol suspension of ultra-fine solid particles or liquid droplets in air
respiratory / salivary from breathing / from spittle/saliva
fecal-oral spread infection caused by oral uptake of fecal matter
venereal infection caused or spread by sexual activity
zoonose infection by microbes or parasites that spread from animals
The simple sketches by the late Stanley Falkow shows the main routes of transmission to and between people. In its simplicity, it reveals one of Stan's great tributes, to streamline and thus make available to all concepts that otherwise may have appeared to be too intricate for a succinct description. With the cacophony of information that bombards us daily about the present pandemic (a pandemonium if there ever was one), Stan is sorely missed by those of us who had heard him make witty but profound statements. How we would benefit from his clarity of mind and his attention-grabbing pronouncements, often expressed with some choice invectives.
We thank Igor Brodsky from the University of Pennsylvania School of Veterinary Medicine, Philadelphia, PA, and Dr. Lucy S Tompkins MD PhD, wife of the late Stanley Falkow, for their permission to use Stanley Falkow's cartoons on these pages. Asked how he came to have the slides, Igor replied:"I was a PhD student with Stanley, and when I left to do my post-doc in innate immunity in the early-mid 2000s, it was before the microbiome became super fashionable and certainly before the general appreciation in the field of immunology for how powerful and fascinating microbial pathogens were. Many (though not all) immunologists still viewed bacteria as bags of LPS for delivering ovalbumin. I asked Stanley for some slides for a presentation that I could give on microbial pathogenesis for immunologists. These were part of his teaching slides for the medical microbiology course and graduate microbial pathogenesis course that he taught at Stanford for many years, and he shared them with me. When Stanley died in 2018, I posted them to my twitter feed to honor and celebrate his legacy of teaching microbial pathogenesis to countless generations of students."