Diseases and cleanliness
TRANSMISSION
Disease pathogens can be transferred from one individual to another in a number of ways - by air, water, food, contact and vectors.
Air is continuously moving around due to temperature changes and air currents. It contains gases, water vapour, microbes, dust particles, etc. An infected individual breathes out air that may contain pathogens and if he or she coughs or sneezes, more pathogens are released. This is especially true in the case of respiratory diseases.
Water supplies are a potential source of disease if they are not purified and/or if there is not a proper sewerage system. In areas where there are open sewers and/or the sewage is untreated, there is serious danger of it filtering into the water sipply and transmitting disease. This is a common situation in many Third World countries.
Food may be contaminated with disease organisms through careless handling and general lack of hygiene. Certain individuals are carriers of diseases, that is they have the pathogens in their systems and, while they do not become ill themselves, can pass the disease on to others: for example, 'Typhoid' Mary, a cook in New York some years ago, was a carrier of typhoid and caused an epidemic through her handling of food. There are legal requirements for hygienic food handling and preparation in most developed courntries but most developing nations have no such regulations or they are not strictly enforced.
Contact between infected and non-infected individuals is a common way in which disease is transmitted. AIDS, some forms of hepititis and genital herpes are mainly transmitted by sexual intercourse, but also by any event during which blood or other body fluids mix. Glandular fever (often called the 'kissing disease') can be transmitted by touching or kissing. Indirect contact may also be a source of pathogens, that is contact with objects used by an infected person, for example bedclothes, towels, showers, etc.
Vectors are organisms that transmit diesease to or between individuals of another species. An example is the transmission of the protozoan plasmodium to humans by the female anopheles mosquito. Plasmodium causes malaria. The vector may simply transfer the pathogens or it may also be a host. In the case of malaria, the mosquito is also a host to the pathogen. Flies, however, transmit disease organisms on the bodies from faeces or other contaminated material without being affected by the pathogens.
THE IMPORTANCE OF CLEANLINESS IN THE CONTROL OF DISEASE
Despite the fact that the Chinese and Hebrews advocated cleanliness as a means of controlling desease as far back as 3000 years ago, humans have been living in unhygienic conditions for most of their existance. Over the centuries humans have not always had access to clean water and soap. They unwittingly passed on pathogens to each other that they did not know existed. Great epidemics wiped out thousands of people even though it was known that being in clease contact with others passed on disease. Even today thousands of people live in crowded conditions with no access to clean drinking water and no facilities for personal hygiene such as the presence of proper toilet facilities.
We know today that sterile condition mean that no microbes are present. We know that microbes live everywhere. They compete with us for food and water. Some microbes use human waste products as sources of nutrients. Not all microbes are pathogenic but pathogenic microbes live in food that has been left in a warm place for some time, in water supplies that have been contaminated with waste (for example sewage) and in human faeces. Because food, water personal hygiene habits are potential sources of infection by pathogens, it is important that they are kept sterile or disposed of in a hygienic matter. Heat, detergents and water, used to achieve cleanliness, kill or remove pathogens.
