A person may be regarded as suffering from a disease when his body does not function properly. Minor and major disorders of the body may lead to diseases. Infectious diseases are caused by germs. One of the greatest achievements in the history of mankind is the demonstration by Pasteur, Koch and others of germs or microbes that cause diseases. Microbes are the microscopic organisms such as virus, bacteria, some fungi and protozoans that are responsible for causing diseases in human beings. Cholera, tetanus, typhoid, diphtheria and pneumonia are some common diseases caused by bacteria. Polio, common cold, influenza, measles, chicken pox and AIDS are diseases caused by virus. Amoebic dysentery and malaria are caused by protozoans.
| Name of the disease |
Medium |
| Tuberculosis, pneumonia, diphtheria, influenza, measles and common cold |
Air |
| Cholera, typhoid, dysentery and diarrhea |
Food, water |
| Leprosy, ringworm and scabies |
Skin contact |
| Malaria, filarial and plaque |
Insects |
