The distribution of time to extinction in subcritical branching processes:Applications to outbreaks of infectious disease

We consider the distribution of the number of generations to extinction in subcritical branching processes, with particular emphasis on applications t o the spread of infectious diseases. We derive the generation distributions for processes with Bernoulli, geometric and Poisson offspring, and discuss some of their distributional and inferential properties. We present applic ations to the spread of infection in highly vaccinated populations, outbrea ks of enteric fever, and person-to-person transmission of human monkeypox. AMS 1991 Subject Classification: Primary 60J80 Secondary 62M05.