Using cure models to estimate the serial interval of tuberculosis with limited follow-up.

Defined as the time between symptom onset of an infector and infectee pair, serial interval (SI) is commonly used to understand infectious diseases transmission. Slow progression to active disease, as well as the small percentage of individuals who will eventually develop active disease, complicate the estimation of the serial interval for tuberculosis (TB). In this paper, we showed via simulation studies that when there is credible information on the percentage of those who will develop TB disease following infection, a cure model, first introduced by Boag in 1949, should be used to estimate the SI for TB. This model includes a parameter in the likelihood function to account for that the study population is composed of those who will have the event of interest and those who will never have the event. We estimated the SI for TB to be around 0.5 years for US/Canada (January 2002 to December 2006) and around 2.0 years for Brazil (March 2008 to June 2012), which may imply a higher occurrence of reinfection TB in a developing country like Brazil.