Delaying the COVID-19 epidemic in Australia: Evaluating the effectiveness of international travel bans

Adeshina Israel Adekunle; Michael Meehan; Diana Rojaz Alvarez; James Trauer; Emma McBryde

We first validate our model by comparing estimates of imported cases provided by the model simulations with reported values as at January 31 st 2020 (see Figure 1 ). We find that our metapopulation model accurately reproduces reported observations for many countries -in particular, Australia -however estimates become increasingly unreliable for countries with significant migration volumes with China. Variation between model predictions and observation can be partially accounted for by stochastic variation and potential under-reporting. 2020, our model estimates that Australia would have received over 70 imported cases of COVID-19 compared with the 15 cases that were actually observed. This represents a 79% reduction in expected cases, and similar to what was estimated elsewhere (6) . However, the introduction of travel bans on international passengers arriving from Iran, South Korea and Italy, does not lead to a significant decrease in the expected COVID-19 importation count to Australia. One reason for this is that the much lower prevalence in these countries compared with China. Furthermore, Italy had already placed itself on lock down by the time Australia enforced restrictions on travelers arriving from Italy. Finally, we explored the effects of travel ban and other intervention -such as reducing contacts to lower the basic reproduction number -on delaying widespread local transmission within Australia. We found that without travel bans, Australia would have experienced local transmission as early as Jan 15 and possibly have become the Pacific epicenter. However, with the China travel ban in place, this delayed the widespread occurrence of local transmission by approximately one month (see Figure 3 ). Thus, if interventions are in place that can reduce the reproduction number to 1.73 (in-line with China's response) local transmission can be further delayed by another 5 weeks (Figure 3 ). Overlaying the simulation prediction with observed local cases in Australia suggesting more needs to be done to slow down the virus in Australia.