PART 3. SPECIFIC DISEASE PROBLEMS

A. PREDOMINANT DISEASES IN THE FOUR MAJOR
TEMPERATURE BELTS OF THE GLOBE

In the geographic distribution of diseases throughout the world, according to the Woytinskys there are four broad regions which follow roughly four separate isothermic paths around the globe. These are:

(1) The temperate climate regions, with the total population of approximately 750 million, form a belt in the Northern Hemisphere, stretching from the United States eastward through Europe over the top of Asiatic Russia to Japan, with the addition of Australia and New Zealand. Here, the most prevalent diseases are heart disease, cancer, tuberculosis, pneumonia, influenza, syphilis, and diabetes.

(2) The tropical belt with over 1,200 million people, or nearly half the population in the entire world, includes a large part of South America and the Caribbean, central Africa, and a great proportion of Asia. These areas are ravaged by malaria, amebiasis, bacillary dysentery, hookworm, yaws, and leprosy. They also suffer from tuberculosis and syphilis.

(3) Between these two belts lies a wide strip that includes the Mediterranean Basin, the Near East, Siberia, Manchuria, and the northwestern part of mainland China, with a total population of approximately 370 million. In addition to the illnesses prevailing in the adjacent areas, this region suffers from dysentery and contagious skin and eye diseases, especially trachoma.

(4) The southern belt includes the extreme southern part of South America and Africa with the population of 80 million. Here, the prevailing diseases are typhoid fever, influenza, tuberculosis, syphilis, and certain worm infections.

NOTE.-Population estimates based on 1950 data.

B. SPREAD OF INFECTIOUS DISEASES

Infectious diseases may be divided into three major groups on the basis of the way the disease is acquired: (1) By exposure to organisms carried in contaminated food or water or found on contaminated soil; (2) by arthropod (insects, ticks, mites, etc.) vectors; (3) by direct contact with other infected individuals (including airborne droplet transmission).

In general, the first group involving contamination of food, water, or soil, is related to poor environmental sanitation-improper disposal of human or animal wastes, lack of water-treatment facilities, and inadequate procedures for handling and protecting food supplies.

The second category, arthropod-transmitted diseases, is related directly to the prevalence and distribution of the various species involved. Generally, this is a function of the climatic conditions favorable to the vectors which prevail, so that many of these diseases are much more important in tropical and subtropical areas.

The third category, the so-called social contact diseases, frequently is related to poor housing which accompanies overcrowding and intimate contact, poverty, lack of personal cleanliness, ignorance, and absence of medical care. In addition to direct control operations, the first and third groups require a well-planned and executed program of health education to assure real progress.