Assessing the delay to detection and the size of the outbreak at the time of detection of incursions of foot and mouth disease in Australia

•Outbreaks of FMD were modelled for 12 geographical regions of Australia.•The time when 95% confidence that a report will be made was calculated.•Both size of outbreak and time to detection showed substantial regional variation.•Up to 53 farms were infected over 43 days before 95% confidence of detection was achieved.

The time delay to detection of an outbreak of an emergency animal disease directly affects the size of the outbreak at detection and the likelihood that the disease can be eradicated. This time delay is a direct function of the efficacy of the surveillance system in the country involved. Australia has recently completed a comprehensive review of its general surveillance system examining regional variation in both the behaviour of modelled outbreaks of foot and mouth disease and the likelihood that each outbreak will be detected and reported to government veterinary services. The size of the outbreak and the time delay from introduction to the point where 95% confidence of detection was reached showed significant (p < 0.05) regional variation with the more remote northern areas experiencing smaller outbreaks that are less likely to spread and less likely to be reported to government services than outbreaks in the more developed southern areas of Australia. Outbreaks in the more densely populated areas may take up to 43 days until a 95% confidence of detection is achieved and at that time, the outbreak may involve up to 53 farms.