Small Lives

 For the past year our macroscopic lives have been dominated by the microscopic: a pathogen that is not by most definitions “life,” though it teeters on the edge. A virus is just DNA or RNA wrapped in protein. By itself it doesn’t do anything. It is great at not doing anything. One dug up in Siberia in 2014 (Pithovirus sibericum) had been doing nothing for 30,000 years, but when introduced to an amoeba it quickly highjacked the cell’s machinery to make more of itself, as viruses do. Few last that long of course. Outside a living organism in exposed environments a virus more typically lasts a few hours – in direct sunlight most (including coronavirus) are destroyed in minutes. Give one a little shade and moisture however, and it can last days. Give it permafrost and apparently it lasts millennia.
 
The overwhelming majority of viruses ignore us. They prefer infecting bacteria or nonhuman large organisms. Even when they hang out inside us, most do nothing. According to biologist Dana Willner at San Diego State University, samples show a healthy human at any moment has on average 174 species of virus in the lungs alone. They do no harm there. Of all the millions of species of viruses in the world, just 263 (depending on how you count different strains of the same virus) are known to affect humans. These can find their way into us in a variety of ways – the nose being a favored but definitely nonexclusive entrance. Counterintuitively, kissing is not very effective for viral transmission, which is probably good news for Valentine’s Day. A University of Wisconsin test of volunteers with colds who tried to infect other volunteers by means of kisses resulted in almost no viral transmission. Droplets from sneezes or from touching one’s own face with contaminated hands are far more effective at spreading colds.
 

Star Trek: "The Immunity Syndrome"

While the mouth (saliva in particular) may be unfriendly to most (not all) viruses, it’s a welcome host to a variety of bacteria and protids. Kissing does transmit these. In fact, a typical French kiss will transfer about 1 billion bacteria between the osculating couple, along with other bits of detritus that it is best not to list. They seldom cause trouble, but they can be bad news when they do. 1,415 are known to cause disease in humans. Once again, that is a tiny percentage of the microbes we encounter, but they are enough. Most of the bacteria and protids inside us are harmless while many are beneficial. In the gut, some are vital for digestion to work properly. Each of us carries trillions of bacterial cells: more than the number of cells that make up our own bodies. Since bacteria are so much smaller than our own cells, however, they account for only 3 pounds (1.35kg) of an average person’s weight.
 
A worrisome trend is that the bacteria that do us harm are growing tougher thanks to our own success in developing (and overusing) antibiotics. This risk was understood very early. In his 1945 acceptance speech for the Nobel prize, Alexander Fleming (discoverer of penicillin) warned that microbes would develop resistance. Germs that are still susceptible to penicillin today sometimes require doses an order of magnitude greater than they did in the 1940s. New antibiotics continue to be developed, but they in turn diminish in effectiveness with use. The day may come when we will need to be as careful of random scrapes and minor injuries as our 19^th century forbearers.
 
In the end, as in the beginning, the world belongs to the microbes. We are the brief interlopers. For the huge majority of earth’s geological history, algae, protids, and bacteria were the only life that existed. When the sun’s evolution makes the earth uninhabitable for large plants and animals (as it will in a few hundred million years regardless of human activity – assuming some other disaster such as an asteroid or supervolcano doesn’t end us first), microbes will be all that remain. They were here before us and they’ll be here after us. Had microbes the capacity to consider us at all, perhaps they would regard us a benign infestation that aids in their reproduction and digestion. They should party it up while the buffet lasts.
 
 

Weird Al Yankovic – Germs