Experimental infectious pancreatic necrosis
infections: propagative or point-source epidemic?
G. Smith, J. Bebak
*
, P.E. McAllister
1
Section of Epidemiology and Public Health, University of Pennsylvania School of Veterinary Medicine,
New Bolton Center, 382 West Street Road, Kennett Square, PA 19348, USA
Received 9 November 1999; accepted 31 August 2000
Abstract
Experimentally initiated epidemics of infectious pancreatic necrosis in rainbow-trout fry were
analyzed using a modification of the standard mathematical model for a simple propagative
epidemic. Contrary to expectations, the value of the transmission parameter (
b
) was inversely
related to initial density of susceptible hosts. This anomaly can be explained if we assume that the
experimental epidemics were point-source rather than propagative epidemics. The implications of
this conclusion for modeling experimental and natural epidemics are discussed.
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2000 Elsevie