Latvia ordered a cull of pigs and a 40-day ban on public events in its eastern district of Latgale on Friday amid an outbreak of African swine fever.
The disease was detected on Thursday evening when three wild boar were found dead by border guards near the Belarus border, the State Food and Veterinary Service said.
Tests showed two of the boar were infected with the disease, which is harmless to humans but lethal to pigs and has no known cure.
The disease is thought to have emanated from Belarus, and was also confirmed earlier this year in wild boar in fellow European Union members Poland and Lithuania.
Russia banned pork imports from the EU on January 29, after Lithuania confirmed the disease in two wild boars.
The EU criticised the move as "disproportionate".
Russia absorbs a quarter of the bloc's pork exports, worth around 1.4 billion euros ($1.9 billion) annually.
Posing a lethal threat to commercial pig farms, African swine fever has spread throughout the Balkans, the Caucasus and Russia since 2007, and is endemic to areas of Africa, according to the United Nations' Food and Agriculture Organisation (FAO).
The FAO warns of "vast losses" if it migrates from Russia to China, which is home to half of the world's pigs.