PERSISTENCE OF INFLUENZA-A BY CONTINUOUS CLOSE-CONTACT TRANSMISSION - THE EFFECT OF NONRANDOM MIXING

The interaction of two populations has variable effects on the nature and duration of epidemic activity, depending on the transmissibility of the virus, the susceptibility of the population, migration, birth and death rates, and the initial number of cases. Under circumstances where transmission stops in a single population (the infectious contact number is less than or equal to one), transmission may continue indefinitely when two populations interact under many different parameter combinations. A mass-action model was constructed using difference equations for two populations that included parameters for migration between populations and variable transmissibility between and within these populations. The limitations of extrapolating the model to actual conditions in human populations result from assumptions inherent in these models, such as fractional infection of individuals.