Key transmission parameters of an institutional outbreak during the 1918 influenza pandemic estimated by mathematical modelling

Table 1 Parameters used in the SEIR incidence model*.

Parameter	Scenario 1	Scenario 2	Scenario 3
Initial proportion of the population susceptible (P_is)	1.0	0.9	0.8
Proportion of infected cases who develop symptoms (P_ids)	0.95	0.81	0.67
Infectivity of asymptomatic/infectivity of symptomatic people (Inf_as)	0.6	0.5	0.4
Proportion of symptomatic cases who present and are diagnosed as infected with influenza (P_sp)	0.95	0.88	0.8

*Based on plausible ranges for pandemic influenza with Scenario 1 being closer to a worse case for impact on health and Scenario 3 being less severe. For example, Scenario 3 assumes 20% of the population may have had immunity from previous influenza pandemics that may have reached New Zealand in the late 19^th century – as suggested by Rice [2] and supported by the unusually low mortality rates in the older age groups for this pandemic in New Zealand [2].

ISSN: 1742-4682