Epidemic - An often sudden increase in the level of disease in a specific population over a given period of time.⏎
Fertilized Egg - Sometimes referred to as a zygote, this is the resulting initial cell formed when a sperm cell unites with an egg cell.⏎
Contagion - A general term for any disease-causing infectious agent spread by direct or indirect contact.⏎
Disease - Any abnormal condition that affects all or part of an organism, resulting in symptoms such as pain or loss of function.⏎