The ongoing Covid-19 pandemic reminds us that the human body can be invaded by a variety of diseases. Covid-19 is caused by a virus that invades the human body. Its symptoms include increased body temperature, nasal congestion, and a sore throat. The severity of those symptoms range from mild to severe, or even fatal. The rate of contagion varies based on geographical location (neighborhood, city, state, nation, globe). Contagion also varies between racial groups (black, white, hispanic, and Asian communities);and between age-groups (fetuses, infants, children, adults, and the elderly). It may also vary based on gender (male, female, transgender) and/or sexual preference (heterosexual, homosexual); or socio-economic class (rich, poor, middle) severity of the symptoms and fatality rates also vary. The most serious widespread viral infections are described as epidemics or pandemics. Covid-19 is now a pandemic. In the United States, bodily viruses are diagnosed and treated by health ca...