Tedros Adhanom Ghebreyesus, the head of the World Health Organization, on Friday wished Donald Trump a swift recovery after the US president and his wife Melania caught Covid-19.
In a tweet, Tedros wished the couple "a full and speedy recovery" as he echoed well wishes from around the world.
Trump is pulling the United States out of the UN health agency, which he accuses of botching its response to the pandemic that emerged in China and being too close to Beijing.
In May, Trump said: "They're a puppet of China, they're China-centric to put it nicer... They gave us a lot of bad advice."
He accused the WHO of "severely mismanaging and covering up the spread of the coronavirus".
Trump charged, among other things, that the outbreak could have been contained "with very little death" if the WHO had accurately assessed the situation in China, where the respiratory disease broke out late last year.
The United States formally started its withdrawal from the WHO in July, making good on Trump's threats to deprive the organisation of its top donor.
Public health advocates and Trump's political opponents voiced outrage at the move.
Throughout the pandemic, Tedros has consistently hit out at divisions in the international community, warning of the consequences of a lack of solidarity.
Against the backdrop of Trump's criticisms, WHO member states in May agreed a resolution calling for an "impartial, independent and comprehensive evaluation... to review experience gained and lessons learned from the WHO-coordinated international health response" to the pandemic.
It said the probe should review WHO's "actions... and their timelines".
The Independent Panel for Pandemic Preparedness and Response is headed by former New Zealand prime minister Helen Clark and former Liberian president Ellen Johnson Sirleaf.
The group intends to produce interim findings in November and a full report in May 2021.