Study: We travel with our own germs

Humans/humanoids have lived for thousands or tens of thousands of years with bacteria, viruses, germs and other critters. They managed to survive for tens of thousands of years. Kudos to our immune system. I'm not going to worry about this.

You're absolutely right, Nightshade 2014. Humans as a species survived; however, statistically they died much younger than we do. A woman's average life expectancy in 1900 was 46. Now, in Japan it's around 87 and a little lower in the Western countries, but still in the 80s.

You're also right not to worry about it excessively. Some exposure builds the strength of the immune system. Still, it helps to understand the importance of good hygiene etiquette, food safety and so on in order to lower one's risk of exposure to serious disease. Even catching a cold is a two-week nuisance that's nicer to avoid.

It's true that bacterial infections and foreign antigens early in life does protect and prepare us for a healthy adult life and that organisms are important to our well-being and that as complex as human biology is it is being more and more recognized literally as human ecology.