It is hard to get infected. The immune system is robust and has a multitude of interlinking defenses that are extremely efficient in beating off most pathogens. Most of the time.
Fortunately, it is a minority of microbes that have evolved to be virulent in humans. Bacteremia is common with our own microbiome. When you brush or floss, bacteria leak into the blood stream:
We identified oral bacterial species in blood cultures following single-tooth extraction and tooth brushing. Sequence analysis of 16S rRNA genes identified 98 different bacterial species recovered from 151 bacteremic subjects. Of interest, 48 of the isolates represented 19 novel species of Prevotella, Fusobacterium, Streptococcus, Actinomyces, Capnocytophaga, Selenomonas, and Veillonella.
but with a good immune system, low virulence bacteria and no place to go, unfortunately the bacteria rarely cause infections.
Even heroin users rarely get infection. Heroin is a rich melange of bacteria and, on occasion, yeasts (I hate to say contaminated, since avoiding microbes is hardly a worry of heroin manufacturers), and the water used for injection is rarely sterile, yet infections are relatively rare despite the filth in which many heroin users exist.
I used to be somewhat fatalistic about hospital acquired infections. However, as the institutions in which I have worked have proven, almost all infections in the hospital are preventable if the institutions aggressively pursue high standards of care.
There are many systems in place in society to prevent infections: flush toilets, good nutrition, public health, vaccines, antibiotics, good hygiene, and an understanding of disease epidemiology, and I suspect people forget there are bugs out there that are pathogenic, just waiting to sicken and kill us. At least a couple of times a year I see patients come into the hospital, previously healthy, who rapidly die of acute infections. But for most people, most of the time, it takes a lot of effort to get an infection.
*This blog post was originally published at Science-Based Medicine*