Viruses can only survive and multiply inside a cell or pathogen. Viruses can invade human cells previously infected with intracellular bacteria, and can also invade and become a bacteriophage of other bacterial pathogens.

Chronic intracellular infections cause chronic disease. When patients with chronic disease develop covid19 the risk for severe disease and virus variants increases. Intracellular co-infections can confuse the immune system; hide the virus; and trigger an increased inflammatory response, to fight a virus inside a bacteria inside a cell.

Co-infections with intracellular bacteria can lead to more severe disease, a more severe inflammatory response, and generation of viral variants.