French Open winner Iga Swiatek is in quarantine after she met Polish President Andrzej Duda who subsequently tested positive for coronavirus.
Mr Duda's diagnosis comes amid a huge surge in the number of confirmed cases of COVID-19 and deaths in Poland, a nation that saw only very low numbers in the spring.
On Friday, Mr Dudda visited the National Stadium in Warsaw, which is being transformed into one of the field hospitals.
He also met Swiatek, the 19-year-old tennis star who won the Roland Garros title earlier this month.
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Swiatek, who was awarded the Gold Cross of Merit for her achievements in sports and promotion of the country internationally, said on Saturday she felt good, but will quarantine.
"Neither I nor members of my team have symptoms of coronavirus. We carry out tests regularly. We will quarantine ourselves in accordance with current procedures," she said in a Twitter post.
Poland is seeing a sharp rise in COVID-19 cases, with new infections hitting a daily record of 13,632 on Friday. The country recorded 13,628 new cases on Saturday.
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