Contagious vs Infectious
An infectious disease is a communicable disease that spreads by contaminating people (or animals) with pathogenic microbial agents, such as viruses, bacteria, or other microorganisms. In other words, a disease where bad germs get into the body in some way, spread, and make you sick by affecting the way your body normally works.
Contagious (or communicable) infections spread through contact. Examples: chickenpox, cold and flu (influenza), malaria, Lyme disease, measles, meningitis, pneumonia, tuberculosis, Ebola, MRSA, polio, hepatitis A and B, HIV/AIDS, and coronavirus.