Question: why do people get ill?

Alexandra Kamins answered on 22 Jun 2010:

All sorts of reasons. People can become ill if they have a “genetic defect,” a simple mistake in the instructions that every cell in the human body carries. These mistakes can do many things, like make the lungs stop working properly in a disease called cystic fibrosis. Or someone can get sick because they eat something that is toxic or poisonous, anything from lead (a metal) to hemlock (a poisonous plant). Lastly, people can get sick because of pathogens–things like viruses, bacteria and parasites.

When someone catches a cold, it means a cold-causing virus snuck by his immune defenses and hijacked cells in his throat! The virus uses the cell to churn out millions of new viruses–it turns your own body cells into virus-making factories. Once there are too many viruses in a cell, the cell explodes and releases all the new viruses out to infect more cells. Sore throats in colds happen because of all of these dying cells in the lining of your throat.

Other symptoms of being sick can be sneaky ways for the virus or bacterium to spread. For example, cholera is spread through the horrible diarrhea it causes. Other pathogens, like the bacterium that causes diphtheria, cause illness because they basically “poop” out a chemical that is toxic while they are growing inside a human. Some symptoms, like a fever, is your body’s own attempt to get rid of whatever is infecting it. A fever raises the temperature higher than many viruses or bacteria like, and they die.