Thanks to Greg Folkers for sending the link to this report from Epidemiology & Infection. The abstract via PubMed: Probable longer incubation period for human infection with avian influenza A(H7N9) virus in Jiangsu Province, China, 2013.
Human infection with the emerging avian influenza A(H7N9) virus in China in 2013 has raised global concerns. We conducted a retrospective descriptive study of 27 confirmed human influenza A(H7N9) cases in Jiangsu Province, to elaborate poultry-related exposures and to provide a more precise estimate of the incubation periods of the illness.
The median incubation period was 6 days (range 2-10 days) in cases with single known exposure and was 7·5 days (range 6·5-12·5 days) in cases with exposures on multiple days, difference between the two groups was not significant (Z = -1·895, P = 0·058). The overall median incubation period for all patients was estimated to be 7·5 days (range 2-12·5 days).
Our findings further highlight the necessity for public health authorities to extend the period of medical surveillance from 7 days to 10 days.