Lithuania, where Tsikhanouskaya lives after fleeing Belarus, requires a 14-day self-isolation period for anyone who has been in contact with someone who has tested positive.
The Belarus opposition leader and all three foreign ministers from Europe's Baltic states have quarantined themselves after meeting with their Slovenian counterpart, who tested positive following a visit to the region this week.
Belarusian opposition leader Svetlana Tikhanovskaya, who lives in exile in Lithuania, had "halted physical contacts" and would be undergoing a test, her press officer, Anna Krasulina, said in a Saturday statement.
"This is not hampering the work of Svetlana Tikhanovskaya’s team," said Krasulina.
"All meetings are now online and preparations are continuing for the People’s Ultimatum on Sunday," she added, referring to Tikhanovskaya's call for a general strike in Belarus aimed at ousting hardline president Aleksander Lukashenko.
Lithuania, where Tsikhanouskaya lives after fleeing Belarus following a disputed presidential election in August, requires a 14-day self-isolation period for anyone who has been in contact with someo ne who has tested positive.
Estonia's Foreign Minister Urmas Reinsalu, Latvia's Edgars Rinkevics and Linas Linkevicius from Lithuania were all reported to be doing fine.
Slovenian Foreign Minister Anze Logar tested positive for coronavirus on Friday after returning from a three-day tour to the Baltic states, where he met with his three counterparts and Tikhanovskaya.
Tikhanovskaya fled to Lithuania following the disputed August 9 presidential election, in which Lukashenko claimed victory despite allegations of widespread vote-rigging.
The United States and the European Union have refused to recognise the presidency of Lukashenko, who has the backing of Kremlin.
Poland's President Andrzej Duda said he tested positive for coronavirus on Saturday just days after he returned from a forum in Estonia's capital Tallinn.
While it was unclear when Duda was infected, he met with Estonian President Kersti Kaljulaid and Bulgarian President Rumen Radev at the forum.
Kaljulaid said on her Facebook page she tested negative for the virus after returning home from France on Friday.
Radev has meanwhile cut short his visit to Tallinn on Tuesday go into quarantine in Sofia.