Estimating infectivity rates and attack windows for two viruses

Cells exist in an environment in which they are simultaneously exposed to a number of viral challenges. In some cases, infection by one virus may preclude infection by other viruses. Under the assumption of independent times until infection by two viruses, a procedure is presented to estimate the infectivity rates along with the time window during which a cell might be susceptible to infection by multiple viruses. A test for equal infectivity rates is proposed and interval estimates of parameters are derived. Additional hypothesis tests of potential interest are also presented. The operating characteristics of these tests and the estimation procedure are explored in simulation studies.