The wild boar, a two-year-old sow, had been struck by a car at Toomja village, Rapla County. Wild boar carrying the disease pass it on to domestic pig stocks.

Maarja Kristian, Veterinary and Food Board (VTA) adviser, the state body responsible for outbreaks, said that the board is monitoring the situation.

Hunters say the news is not good.

"This is very bad news for hunters; we were so hopeful that we would soon be able to get our forests free and return to a normal life," said Margus Puust, president of the Estonian Hunters' Association (Eesti Jahimeeste Selts).

Maarja Kristian said that the find was significant in that the animal displayed the actual virus, rather than just antibodies; the first find of its kind in around 18 months.

In June, the state had been applying to the European Commission for ASF-free status, an accolade it had received from The World Organisation for Animal Health (OIE) in January.

The VTA requests hikers, berry and mushroom pickers, hunters and anyone else spending time in the forest to contact the nearest county center if they find a dead wild boar.

Pig farms have been clear of the virus for three years, but the incident reveals the threat has not completely gone away.

New ASF outbreaks are reported almost daily, Europe-wide, with cases in Latvia, Lithuania, Poland, Ukraine and several other, mainly central and eastern European countries.

Domestic pigs may not be kept outdoors in Estonia, nor may they be fed food waste, under VTA rules, as a precaution against ASF.

The VTA also asks those heading for the forest not to discard food waste there, for the same reason.