ALL the items can cause illness in some way or the other.
Water: If water is dirty and contains germs in it, it is not safe to drink. If anyone drinks it, they can get ill.
viruses, such as those that cause the common cold : These viruses are communicable and can spread to other people as well.
bacteria, such as E. coli : Though this bacteria normally lives in the intestines of healthy people and animals. But its few strains can cause severe abdominal cramps, bloody diarrhea and vomiting.
coughing on a person when you are sick : If a person is suffering from cough and he coughs on another person, then that person can also get ill.
forgetting to wash your hands : Our hands contains germs as we always touch one thing or the other, If we eat by dirty hands, we can get stomach illness.
eating contaminated : Contamination in water or food can get anyone severely ill.
