Computer simulation of Gumboro disease outbreak. III. Construction model G-4.

Following the simulation mode., G-3, of Gumboro disease outbreak, Model G-4 was constructed. The algorithm for computer simulation is shown in a flow chart. The postulates added to those for Models G-1 and G-2 are as follows: (1) The source of contamination is the virus remaining in the house and declining gradually in value with the lapse of time. (2) Any diseased bird excretes the virus during a certain period, so that the virus may be added to the source of contamination. (3) The morbid status of the diseased bird becomes worse in process of time, but the infection remains subclinical until a threshold value is reached. Beyond this value the bird becomes clinically diseased. In this model, more than 20 parameters are involved, and random numbers used for expressing the individual differences in the four variables, viz., the level of innate resistance, parentally conferred immunity, virus-intake, and threshold of clinical manifestation.