Vaccines
Vaccines are harmless derivatives of pathogenic microbes that stimulate the immune system to mount defenses against the harmful pathogen
Epidemic
outbreak of disease that spreads quickly and affects many individuals at the same time
Pandemic
Global Epidemics
Viroids
Viroids are small circular RNA molecules that infect plants and disrupt their growth
Prions
Prions are slow-acting, virtually indestructible infectious proteins that cause brain diseases in mammals