Send to

Choose Destination
Epidemiol Infect. 2007 Oct;135(7):1145-50. Epub 2006 Dec 7.

Infectiousness of smallpox relative to disease age: estimates based on transmission network and incubation period.

Author information

Department of Medical Biometry, University of Tübingen, Tübingen, Germany.


This study investigated the infectiousness of smallpox relative to the onset of fever using a likelihood-based estimation procedure based on the observed transmission network (n=223) and on the distribution of the incubation period (n=379). Who-infected-whom information enabled us to back-calculate the infectiousness by disease age, employing a step function model for infectiousness. Frequency of secondary transmissions was highest between 3 and 6 days after onset of fever, yielding an expected daily frequency of 20.6% (95% CI 15.1-26.4) of the total number of secondary transmissions, which is consistent with previous observations. The estimated cumulative frequency suggests that 91.1% of secondary transmissions occurred up to 9 days after onset of fever. The proposed method appeared to be useful for diseases with an acute course of illness, where transmission was not hampered by depletion of susceptible contacts.

[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Cambridge University Press Icon for PubMed Central
Loading ...
Support Center