File photo: AFP

GENEVA, Oct. 2 (Xinhua) -- The head of the World Health Organization (WHO) on Friday expressed his best wishes to U.S. President Donald Trump and First Lady Melania Trump, who have tested positive for COVID-19, for a full and swift recovery.

"I wish them both a full and swift recovery. Our prayers are with them," said WHO Director-General Tedros Adhanom Ghebreyesus at the start of a press briefing on Friday.

Trump tweeted early Friday morning that he and his wife had tested positive for COVID-19.

Also at the press briefing, Michael Ryan, executive director of the WHO Health Emergencies Program, said: "WHO absolutely trusts the U.S. public health authorities to make appropriate decision."

Ryan noted that there's clearly a cluster of cases occurring in the Trump scenario, which needs to be properly investigated.

On the COVID-19 situation in the U.S., Ryan said: "there's no reason why the U.S. cannot control this disease, turn the corner, and get the disease under control." But that requires work, effort, commitment, transparency and honesty, as well as sustained support to get that job done.

"We want all public leaders, particularly leaders of great countries, to lead us and give us hope, and to give us certainty, to give us truth, and to give us a chance to fight and win this disease," he added.

"It is never, ever too late for that to be true. I hope that all leaders around the world in health, in medicine, in politics reflect upon what we're all facing, and that we can all come together to fight this disease," Ryan stressed.

As the world is in the midst of the COVID-19 pandemic, countries across the globe -- including UK, China, Russia, Britain and the U.S. -- are racing to find a vaccine. According to the website of the World Health Organization (WHO), as of Sept. 30, there were 192 COVID-19 candidate vaccines being developed worldwide, and 41 of them were in clinical trials.