But however secure and well-regulated civilized life may become, bacteria, Protozoa, viruses, infected fleas, lice, ticks, mosquitoes, and bedbugs will always lurk in the shadows ready to pounce when neglect, poverty, famine, or war lets down the defenses.
—
Hans Zinsser
![“It is with the [head louse and body louse] that we are chiefly concerned, and they are so closely related that, even now, by an occasional mésalliance resulting from the meetings of young people about the neck band, a body louse may go native and interbreed with a head louse. The crab louse we may…” quote by Hans Zinsser](https://sms4smile.com/quotes/img-quotes/7d6/hans-zinsser-34557_young-people_it-is-with-the-head-louse-and-body-louse_1442761.jpg)
![“... [I]nfectious disease is merely a disagreeable instance of a widely prevalent tendency of all living creatures to save themselves the bother of building, by their own efforts, the things they require. Whenever they find it possible to take advantage of the constructive labors of others, this is…” quote by Hans Zinsser](https://sms4smile.com/quotes/img-quotes/0c7/hans-zinsser-34557_advantage_i-nfectious-disease-is-merely-a-disagree_1503200.jpg)
![“Medical historians have cited many observations which they regarded as indicating the ancient existence of syphilis; but most of these, on close scrutiny, turn out to be unconvincing […] Ozanam quotes two sonnets from a Florentine poet—one entitled ‘De Matrona,’ the other 'Ad Priapum'—which he…” quote by Hans Zinsser](https://sms4smile.com/quotes/img-quotes/0f5/hans-zinsser-34557_history_medical-historians-have-cited-many-obser_1854315.jpg)
