Introduction
African swine fever (ASF) is a highly contagious disease affecting pigs.
It is caused by African swine fever virus (ASFV), which belongs to the
genus Asfivirus of the Asfaviridae family (Alonso et al., 2018). ASF can
spread through direct or indirect contact and causes high mortality. The
ASFV persists for a long time in the environment and in a variety of pig
products. Wild boar can harbor the virus and ASF may become endemic with
or without an added transmission cycle through Ornithodoros ticks
(Plowright et al., 1994). Traditionally ASF was confined to Africa, with
occasional incursions into other regions until in 2007 when ASF was
introduced into Georgia, a Caucasus country (Sanchez-Vizcaino et al.).
From Georgia, the disease spread to other Caucasus and East European
countries (European Food Safety Agency, 2010). Since ASF was reported in
China for the first time in August 2018, it not only spread to within
the country but to other Asian countries. Japanese pig population is
petentially at risk of getting infected with ASFV as a result of being
fed illegally imported pork products from ASF-affected countries
(Sugiura et al., 2018). Based on this assumption, we have previously
assessed the risk of ASF introduction into Japan through pork products
illegally imported from China and fed to pigs as swill, using a
stochastic model and the latest data available up to 2019 (Sugiura et
al., 2020). As a result, the annual probability of ASFV entry into Japan
via this pathway was predicted to be 20% (90% prediction interval:
0–90%) (Sugiura et al., 2020). However, under the various
interventions taken to manage the human coronavirus outbreak that
started in late 2019, there have been substantial changes in the value
of some of the variables used in the model. These include the number of
air travelers from China and the amount of food waste from restaurants.
In this study we attempted to predict the change in the ASF entry risk
into Japan after January 2020 due to the changes in these variable
values under the coronavirus pandemic.