Highly pathogenic avian influenza virus infections in mammals: patterns, predictions, and implications for human epidemics

The continuing spread of avian influenza virus through the animal kingdom, particularly, in mammals, represents an imminent worldwide threat with the potential to mutate into a significant human pandemic. We recognized the need for tools to quantitatively describe and predict the courses of sequential individual waves of infection in mammals to facilitate future allocation of resources for combating the spread. Using public data from the US Department of Agriculture for about a 2-year period, we showed that the Gompertz equation is an effective tool for describing each of the three epidemic waves during that period. The nature of these regression equations is that early data can be used to predict the number of future cases, time course, and inflection point of individual waves. In comparing the parameters of the resulting regressions, we noticed that the waves became more exponential in character and less sigmoidal (less tendency to level off) as they progressed in time.