A communicable disease is a disease that can spread from one person to another through a germ or its toxic product from an infected person, animal or reservoir.
The transfer of this infectious germ can be direct by consumption of contaminated food or water OR indirectly through intermediate animals/plants, vector (e.g. mosquitoes) or in-animate objects such as handkerchiefs, door handles, cups etc.
1. Lack of potable water
Good water supply prevents a lot of communicable diseases such as cholera, hepatitis A, typhoid fever, diarrhoeas and dysentery. These are classified as water-borne diseases. Consequently they are common in poor developing countries where potable water is in short supply and the people are un-aware of such simple procedure as boiling water for drinking.
2. Lack of sanitary facilities
Open defeacation is quite common in poor countries around the world. About half the population of India has no access to toilet facilities—600,000,000 (six hundred million) people. In Nigeria, less than 60% of the population has access to toilet facilities. Water is therefore easily contaminated by shit (feaces) in these countries, if taken without boiling or treatment a communicable disease such as cholera could be contracted.
Vegetables and fruits could also be easily contaminated in these countries and if not properly prepared before eating, communicable diseases such as poliomyelitis and typhoid fever could be contracted.
3. Poor Sewage and Refuse Disposal System
Poor refuse disposal system encourages the breeding of rats and flies. Exposed food can be contaminated by feaces through flies, rats are associated with some diseases such as Lassa Fever and plague.
Poor sewage disposal system means dumping of sewage into the open and/or into rivers which could be sources of drinking water.
Drinking such water without treatment is a recipe for disaster.
4. Poor Food hygiene
Food hygiene involves proper handling of uncooked food, proper preparation of vegetables and fruit for eating. It also involves proper cooking of food and proper storage after cooking if not eaten immediately. These measures are very necessary in poor countries where open defeacation is common.
5. Poor Housing
Poorly ventilated houses encourage the spread of communicable diseases such as meningitis, pneumonias, TB, measles, and other air-borne diseases.
6. Poor personal hygiene
Poor personal hygiene promotes the spread of some communicable diseases. Personal hygiene involves the washing of hand after using the toilet, sneezing into handkerchiefs rather than into the open, same for coughing; washing your hand after sneezing. The use of sanitizers is also advised.
Good personal hygiene breaks the transmission of diseases such as Ebola Virus Infection and Typhoid fever.
7. Low socio-economic Status
Low socio-economic status is a risk factor for some communicable diseases, low socio-economic status means poverty, unemployment, marginalization, illiteracy etc.
Those in this group are more prone to TB, measles, sexually transmitted diseases and tetanus just to name a few.
Environment plays a big role in communicable diseases. Some are more common in the raining season, while others are more common during the dry season. Some communicable diseases are more common in the rural areas while others are commoner in peri-urban or urban slums.
Location of certain business undertakings in certain localities increases the risk of certain communicable diseases such as sexually transmitted diseases such as gonorrhea. This is social environment.