Answer:
You can get an infectious disease which are caused by organisms. They may spread in a number of ways:
1) In infected water e.g. Choleria bacteria.
2) By direct contact (contagious) e.g. head lice - insects.
3) By animal vectors e.g. Plasmodium.
4) In dropkets in the air e.g. influenza virus.
5) In contaminated food (causes food poisoning) e.g. Salmonella bacteria
6) Via body fluids e.g. Hepatitis B virus or HIV.