Germany is on red alert after new cases of African swine fever in neighboring Poland and the Czech Republic increased the risk of the deadly disease crossing the border.

There was a particular risk of humans carrying the disease across the border, a spokeswoman for Friedrich Loeffler Institute (FLI), a federal research body for animal health, said on Tuesday.

Of particularly high risk are food scraps collected for disposal from motorway service stations, she said.

The disease has made its way westward from Georgia and Russia across the EU's eastern borders, now affecting six EU countries.

African swine fever poses no risk to humans but is nearly always fatal for pigs and wild boars and there is no vaccine against it. A serious outbreak could lead to huge financial losses for pig farmers.

There have been 279 new cases of the disease in Poland between the end of November and the start of January, and the disease appears now to have spread to the west of the capital Warsaw, the FLI said, describing the situation as alarming.

In the Czech Republic, there have been 25 new cases concentrated near the Slovakian border.

In the past year there were 248 cases in domestic pigs and 3,859 in wild boars in the Baltic States, Ukraine, Romania, Poland and the Czech Republic, the FLI said, adding there was no end to the outbreak in sight.