|
|
Bacteria have flourished on the earth for over three billion years. They were the first life forms on the planet.
Autoimmune diseases occur when the immune system destroys its own healthy tissues. When this occurs, white blood cells cannot distinguish between pathogens and normal cells.
Vaccines prevent between 2.5 and 4 million deaths every year.
Only 12 hours after an egg cell is fertilized by a sperm cell, the egg cell starts to divide. As it continues to divide, it moves along the fallopian tube toward the uterus at about 1 inch per day.
The Centers for Disease Control and Prevention (CDC) was originally known as the Communicable Disease Center, which was formed to fight malaria. It was originally headquartered in Atlanta, Georgia, since the Southern states faced the worst threat from malaria.