The immune system has difficulty fighting intracellular pathogens; and in response to intracellular pathogens and the abnormal proteins generated by the pathogens, the immune system generates a cascade of immune defenses, i.e. the war within, which include a high level of inflammation and generation of adhesion molecules. The immune system attack may be diagnosed as a chronic disease; an autoimmune disease; or in acute disease, as the immune system generating a higher level of damaging inflammation, for unknown reasons.
U.S. physicians are discouraged from testing for chronic infections due to the cost of testing, lack of recognition of the importance of testing, and lack of available testing for many different pathogens at the same time. In Brazil, a high rate of underlying chronic intracellular infections, originating in pets and animals, has been reported, which may explain why particular variants of covid19 emerged in Brazil; and explain how similar variants arose in other parts of the world where similar underlying infectious pathogens are common in the population.
If physicians had the tools to diagnose many different pathogens in one blood test, and/or routinely diagnosed intracellular pathogens in patients with acute and chronic disease, we would better understand the most common pathogens present in patients around world, causes of chronic disease, and how and where viral variants may evolve.