Infectious diseases are caused by germs (bacteria and viruses). A bacteria is a microscopic creature consisting of a single very simple cell which does not have anything complex like a nucleus inside it. A virus is a tiny microscopic infectious agent that can only increase in numbers (multiply) inside living cells of a plant or animal. Bacterial and viral infectious diseases spread directly or indirectly from person to person, for example through coughing up germs. They are all conditions that you catch.
Parasites are microscopic creatures that cause diseases, and worms, large and small, that cause diseases.
Of the deaths recorded here; 27% of deaths were caused by HIV/AIDS, 17% by diarrhoeal diseases , 14% by Tuberculosis, 8% by malaria, and within the childhood-cluster diseases 6% by measles and 3% whooping cough and 2% by tetanus. Also causing 2% of these deaths each were Sexually transmitted diseases and meningitis. All other categories were under 2% each.
These infectious and parasitic diseases caused 19% of all deaths worldwide in 2002, an average of 1766 deaths per million people. In the territory with the highest rate of deaths, Botswana, with 19642 deaths per million people, 95% were caused by AIDS. AIDS caused about 85% of deaths in the next 3 highest territories, Lesotho, Swaziland and Zimbabwe.