Definition from Wiktionary, the free dictionary
- (pathology) In epidemiology of communicable (infectious) diseases, the time period between the onset of symptoms with the primary patient and the onset of symptoms with the secondary patient (infected by primary).
- Daryl J. Daley. Epidemic Modelling: An Introduction, Cambridge University Press, 1999, p. 17. 
- Transmission Dynamics and Control of Severe Acute Respiratory Syndrome