Mariefred working group - SARS

Other groups : Contact structures Model selection and Bayesian inference Vaccination issuess Endemicity

Epidemics home page Mariefred 2003 Participants with email addresses Postal addresses

Coordinator: Jacco Wallinga (RIVM, Bilthoven)

The group on SARS modelling consists of Åke Svensson, Gianpaolo
Scalia-Tomba, Philip O'Neill, Kari Auranen, Christophe Fraser, Pieter
Trapman, Niels Becker, Denis Mollison and Jacco Wallinga.

There are three issues where some progress can be made such as to help
modelling and decision-making in a future outbreak of an emerging outbreak
of an infectious disease:

1) asymptomatic transmission. When can one state that with a probability
of, say, 0.95 the value of the reproduction number has dropped below one,
and one can one state that with a probability of 0.95 the epidemic is over?

2) modelling contact tracing. For which infections will it be possible to
find infecteds by contact tracing in time? It is relatively easy to write
down algorithms and do a simulation study, but obtaining exact results
appears very hard.

3) estimating characteristics of spread such as the logarithmic growth rate
r and reproduction number R. One can proceed by fitting detailed
transmission models of the infection to observations (a highly parametric
approach), or by directly estimating the realised growth rates and
reproduction numbers with few assumptions about the exact transmission
process (a semi-parametric approach). Which approach is more efficient and
more precise?

Some appropriate references:

M.Eichner & K.Dietz (1996) Eradiction of poliomyelitis: when can one be
sure that polio virus transmission has been terminated? American Journal of
Epidemiology 143:816-822

J.Müller, M. Kretzschmar & K. Dietz (2000) Contact tracing in stochastic
and deterministic epidemic models. Mathematical Biosciences 164: 39-64.

S. Riley et al. (2003) Transmission dynamics of the etiological agent of
SARS in Hong Kong: impact of public health interventions. Science 300:

M. Lipsitch et al. (2003) Transmission dynamics and control of severe acute
respiratory syndrome. Science 300: 1966-1970.

We have identified some issues concerning the SARS outbreak in 2003 that
are beyond our grasp: making the data on SARS outbreaks available for all
research groups, and analysing the data on SARS outbreaks in hindsight.
More important, we have identified

Niels will try to get some grip on the issue of asymptomatic transmission,
and send a manuscript about this to the other members. Christophe will try
his hand on modelling contact tracing, and send a note to the others. Jacco
will send a manuscript on direct estimation of reproduction numbers to the
other group members.

Maintained by Denis Mollison

8th September 2003