Slovakian Prime Minister Igor Matovic is urging people to be "extremely careful" after testing positive for coronavirus.
Another EU leader has tested positive for coronavirus after attending a summit in Brussels last week.
Slovakian Prime Minister Igor Matovic confirmed his COVID-19 diagnosis on Friday - a day after French President Emmanuel Macron also revealed he had contracted the disease.
"I'm one of you today," Matovic wrote in a Facebook post as he described the "tension and fear" he felt while awaiting a text message with his test result.
"Please be extra careful. I know that looking at a stranger as a number in line is a comfortable and popular thing with many people nowadays.
"But people are not numbers and no grandma or grandpa deserves our selfishness. No chronically ill person deserves to be despised and considered inferior in their life, just because we are supposedly ′free'. No, we are not!"
Matovic was originally planning to spend Christmas volunteering at a hospital, but admitted this was looking "a little different now" as he apologised for being "[an elephant in a china shop] making mistakes".
The 47-year-old's announcement comes a little over 24 hours after the Elysée Palace also confirmed Macron's diagnosis.
On Friday, officials said the French president had developed a cough, fever and fatigue, and was self-isolating at the La Lanterne residence in Versailles.
They declined to comment on any treatment he would be receiving.
While Macron has had several recent meetings in Paris, France's health minister has suggested that he may have actually caught COVID-19 at an EU summit in Brussels last week - the same summit attended by Matovic.
It is not yet clear who else - if any - at the event was in close contact with Matovic, although back home, Slovakian media has reported several ministers are now quarantining.
Meanwhile, European Council President Charles Michel, Spanish Prime Minister Pedro Sanchez and Portuguese Prime Minister Antonio Costa are all in isolation after meeting with Macron this week.
Belgium Prime Minister Alexander De Croo and Luxembourg Prime Minister Xavier Bettel are also in quarantine awaiting a test result after the EU summit, while European Commission President Ursula von der Leyen is not planning to isolate after testing negative.
Which European leaders have had COVID-19?
Nikol Pashinyan, prime minister of Armenia
Alexander Lukashenko, president of Belarus
Boyko Borissov, prime minister of Bulgaria
Andrej Plenković, prime minister of Croatia
Emmanuel Macron, president of France
Albert II, prince of Monaco
Andrzej Duda, president of Poland
Igor Matovic, prime minister of Slovakia
Boris Johnson, prime minister of the UK