Key transmission parameters of an institutional outbreak during the 1918 influenza pandemic estimated by mathematical modelling.
OBJECTIVE
To estimate the key transmission parameters associated with an outbreak of pandemic influenza in an institutional setting (New Zealand 1918).


METHODS
Historical morbidity and mortality data were obtained from the report of the medical officer for a large military camp. A susceptible-exposed-infectious-recovered epidemiological model was solved numerically to find a range of best-fit estimates for key epidemic parameters and an incidence curve. Mortality data were subsequently modelled by performing a convolution of incidence distribution with a best-fit incidence-mortality lag distribution.


RESULTS
Basic reproduction number (R0) values for three possible scenarios ranged between 1.3, and 3.1, and corresponding average latent period and infectious period estimates ranged between 0.7 and 1.3 days, and 0.2 and 0.3 days respectively. The mean and median best-estimate incidence-mortality lag periods were 6.9 and 6.6 days respectively. This delay is consistent with secondary bacterial pneumonia being a relatively important cause of death in this predominantly young male population.


CONCLUSIONS
These R0 estimates are broadly consistent with others made for the 1918 influenza pandemic and are not particularly large relative to some other infectious diseases. This finding suggests that if a novel influenza strain of similar virulence emerged then it could potentially be controlled through the prompt use of major public health measures.
Sertsou
Gabriel
G
Department of Public Health, Wellington School of Medicine & Health Sciences, University of Otago, Wellington, New Zealand. gabriel.sertsou@otago.ac.nz
Wilson
Nick
N
Baker
Michael
M
Nelson
Peter
P
Roberts
Mick G
MG
D000328:Adult; D002423:Cause of Death; D004196:Disease Outbreaks; D049673:History, 20th Century; D006772:Hospitals, Military / Q000706:statistics & numerical data; D006801:Humans; D007251:Influenza, Human / Q000266:history / Q000401:mortality* / Q000635:transmission*; D008297:Male; D008889:Military Personnel; D008962:Models, Theoretical; D009520:New Zealand / Q000453:epidemiology; D018410:Pneumonia, Bacterial / Q000209:etiology / Q000401:mortality; D014774:Virulence