Final multivariable Cox proportional-hazards survival model describing variables associated with outbreak duration.

n = 136 observations; log-likelihood = −532.25.The hazard ratio represents the effect of a unit change in the explanatory variable on the frequency of the outcome, which in this case is the last case of an outbreak. If the hazard ratio for a variable is greater than 1.00, an increase in the variable results in an increase of the hazard. In other words, when the value of the variable increases, an outbreak is expected to be of a shorter duration.