Communicable diseases, such as schistosomiasis (bilharzia), are transmitted by vectors which depend on water.
Their involvement previously has been confined to communicable diseases.
It is transmitted via the respiratory route, is highly communicable and mainly affects young children.
But communicable diseases must be controlled to improve public health.
Identifying the agents of communicable diseases was only one step to finding a cure, and the next step was often many decades away.
This increase might be the result of cumulative exposure over the years, and is expected in endemic areas in the case of most communicable diseases.
In general, transmissible agent, host and environment are the three factors that affect the epidemiology of communicable diseases.
The authorities hired physicians as gatekeepers to identify desirable and undesirable traits that went beyond the definition of communicable disease.
