It is interesting to learn that climate is not the direct cause of an ailment or disease. However, a certain combination of climatic elements may alter or affect the metabolism, respiration or circulation of an individual. It may strengthen or weaken his resistance to various types of diseases.
In fact, individual cleanliness, his foods, physical activity and several such social factors determine the incidence and spread of a disease. There are two climatic influences on disease.
The climatic elements directly affect the disease organism because of their association with temperature, moisture and other climatic requirements of microscopic organisms. The type of influence is the effect of weather and climate on the body’s resistance.
Certain diseases are, indeed, associated with certain climates or with a particular season. Malaria spread by certain species of mosquitoes that thrive in tropical climates is a typical example.
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Scarlet fever is rare in tropical countries. Leprosy is common in the tropics and subtropics. Actually some diseases are spread by certain organisms that carry them. Such disease carriers are confined to those areas where they find favourable conditions of temperature, moisture and other climatic requirements.
There are certain diseases which are closely associated with seasons. Pneumonia, influenza, measles and scarlet fevers may be cited as some of the examples. Measles in the tropical countries occur mostly in the spring season.
The greater incidence of diseases like influenza and pneumonia in winter is on account of the lowered resistance of the body, particularly that of the upper respiratory tract.
The incidence of infectious diseases is more common in winter and spring. Sudden changes in weather may be followed by outbreaks of sickness. Those with poor resistance in their bodies fall an easy victim to such types of ailments.
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There are many other kinds of associations between weather conditions and the occurrence of various diseases. These associations are, indeed, very difficult to explain. Asthma, for example, has the closest links with weather conditions.
Derrick demonstrated the relation between seasonal and annual variations of asthma cases in Brisbane. He came to the conclusion that there was a significant correlation with the temperature, and the high- asthma weeks were associated with a rapid fall in the mean and minimum temperatures, dew point, humidity and the amount of rainfall.
The increase in illness usually occurred within 48 hours of the fall in minimum temperature and relative humidity. Sudden changes of atmospheric pressure also are the cause of ailments like duodenal ulcers and peripheral arterial embolism. Sudden falls in temperatures are equally harmful to the patients suffering from such ulcers.
There is no doubt that there is a close relationship between health, disease and man’s economic activity. Thus it is evident that the variations in the atmospheric resource such as those produced by man-made pollution, through their effects on health and disease must have a direct impact on economic activities of man.