The behaviour of three viruses, rinderpest, Newcastle
disease, and Rift Yalley fever, in different hosts has been
statistically appraised. The population patterns were
characterised by a sequence of lag, expansion, peak and
decline phases. Increase and decrease in the populations
vers exponential. A complete curve was associated with
recovery of the infected host. Deaths terminated the
sequence but never during the lag phase nor in the early
part of the expansion phase.
Two parameters, the rate of increase and the curvature,
were found to be constants. They were independent of the
strain and dose of virus. They were independent of the
host and the tissue sampled. Moreover, only minor differences in the rates occurred between virus species.
Two parameters, the length of the lag phase and the
peak titre, varied. The former was inversely related to
the concentration of infective virus in the dose. The
latter was directly related to adaptation to the host.