The disease, which kills nearly all pigs that catch it, was discovered in Russia early in October, but has since spread considerable distances and has recently been confirmed close to the EU border.
A report by Defra said the disease had now been discovered near Leningrad and was just 200km from the EU border. It said there was little risk of the disease entering the UK through livestock movement, due to prohibits on the trade of susceptible animals and their products from Russia.
However, the report said: "Nevertheless, this outbreak may have increased the overall low risk of the disease introduction to the UK (and the EU) by other possible pathways, given that the disease has now been reported in an area that is geographically relatively close to the EU, compared to the affected areas in the Caucasus region.
"The likelihood of the introduction of the virus by illegal imports remains difficult to estimate. This emphasises the importance of appropriate disposal of international catering waste from ships and aircraft, and having vigilant enforcement agencies at the border. This outbreak highlights again the importance of maintaining strict biosecurity measures at pig farms, prompt reporting of suspected cases and the current prohibition of swill feeding in the UK (and the EU)."
Scientists at the BBSRC's Institute for Animal Health (IAH), and the UN's Food and Agriculture Organisation (FAO) said that the ASF threat should be taken seriously. It said the virus can survive for months in cold meat store and for years in frozen carcases.
There is no vaccine against ASF; attempts to make one by conventional means have not been successful. Control of the disease is by slaughter and strict adherence to movements on and off farms.