Trump’s announcement Friday, on Twitter, that he and first lady Melania Trump tested positive for the coronavirus, and the deep uncertainty that accompanied it, upended countless plans and sparked comment everywhere from presidential offices to the thousands weighing in on social media.

The positive test reading adds more uncertainty to investors’ worries, especially about its effect on the Nov. 3 election between the Republican president and Democrat Joe Biden. U.S. stock futures and most world markets fell on the news as did the price of oil.

World leaders were quick to offer official sympathy from the top, while something approaching schadenfreude bubbled up from elsewhere. Trump joins a growing list of the powerful who have contracted the virus, including many who were skeptical of the disease.

“I’m sure that your inherent vitality, good spirits and optimism will help you cope with the dangerous virus,” Russian President Vladimir Putin wrote in a direct message to Trump released by the Kremlin.

World Health Organization director-general Tedros Adhanom Ghebreyesus tweeted “My best wishes to President @realDonaldTrump and @FLOTUS for a full and speedy recovery.” The Trump administration in July formally notified the United Nations of its withdrawal from WHO, although the pullout won’t take effect until next year. Trump claims the U.N. health agency is in need of reform and is heavily influenced by China. The U.N. secretary-general also sent in best wishes.

Italian right-wing opposition leader Matteo Salvini tweeted: “In Italy and in the world, whoever celebrates the illness of a man or of a woman, and who comes to wish the death of a neighbor, confirms what he is: An idiot without soul. A hug to Melania and Donald.″

British Prime Minister Boris Johnson, who was hospitalized for a week in April after he contracted COVID-19, wished Trump a “speedy recovery.”

Dr. Bharat Pankhania, who advises Johnson’s government on communicable disease control, said he hopes that Trump’s positive test sends a message to the president and other leaders.

“We need politicians, especially politicians like President Trump who has a lot of power and influence, to take this seriously and to support their scientists and clinicians in leading the outbreak management, rather than have political influence in trying to deny that this virus is in circulation and drag your feet around control measures because it suited your agenda.”

Tokyo Gov. Yuriko Koike, speaking at a weekly news conference, did not mention Trump’s reluctance to wear masks when asked about his infection, but she said the news “reminded me of how widely masks are worn in Japan.”

Major media across the globe also played up the announcement, with bulletins crawling across TV screens in Seoul, Tokyo, Taipei, Dubai and Beijing.

“To say this potentially could be a big deal is an understatement,” Rabobank said in a commentary. “Anyway, everything now takes a backseat to the latest incredible twist in this U.S. election campaign.”

China’s official Xinhua News Agency flashed the news, and an anchor on state broadcaster CCTV announced it; there was no immediate comment from the government Friday, the second day of an eight-day national holiday.

The positive test result for Trump and his wife was the most searched topic in China on the widely used social media app Weibo a few hours after the announcement, with most comments mocking or critical.

One user darkly joked that Trump had finally tweeted something positive.

The Chinese government has bristled at Trump’s attempts to blame China, where the disease emerged, for the pandemic and called for global cooperation in fighting it, a message that has resonated with the public.

Hu Xijin, the outspoken editor of the state-owned Global Times newspaper, tweeted in English that “President Trump and the first lady have paid the price for his gamble to play down the COVID-19.”

Multiple Arab news media outlets on Friday continuously broadcast footage of Trump and his wife after the virus announcement.

Al-Arabiya, a Saudi-owned satellite channel based in Dubai, cut to a long live shot of the White House. Qatari state-owned Al Jazeera channel brought in four commentators to discuss the “prevailing state of uncertainty” in the United States, questioning whether Trump could effectively steer a reelection campaign and run the country from quarantine.

Iranian state television announced Trump had the virus, an anchor breaking the news with an unflattering image of the U.S. president surrounded by what appeared to be giant coronaviruses. U.S.-Iran ties have suffered since Trump unilaterally withdrew the United States from Tehran’s nuclear deal with world powers and reimposed crushing sanctions.

Social media platforms were ablaze with quick reaction.

Would Trump blame the Chinese? Would he thumb his nose at his critics and enemies by breezing through the quarantine without serious symptoms, tweeting away from the White House? Would he become gravely ill, or worse, and, if he did, what would that mean for the U.S. election, one of the most contentious in recent history? What would it mean for U.S. leadership during tumultuous times?

While the uncertainty seemed palpable on a scroll through various social media in an array of languages, many comments seemed to revel in the announcement.

“Here comes a chance for him to actually try out his idea of injecting disinfectant into himself and fighting back (against allegations that) it was fake news!” tweeted Hiroyuki Nishimura, a Japanese internet entrepreneur, referring to an idea Trump floated earlier this year for treatment.

And the satirical Australian news site, the Betoota Advocate, posted a story with this headline: “Trump Family Records More Cases Of Community Transmission Than Entire State Of Queensland.”

Lori Hinnant reported from Paris. Associated Press writers Danica Kirka in London, Nasser Karimi in Tehran, Iran, Ashok Sharma in New Delhi, Ken Moritsugu in Beijing, Jon Gambrell in Dubai, United Arab Emirates, Rod McGuirk in Canberra, Australia, Mari Yamaguchi and Elaine Kurtenbach in Tokyo, and Colleen Barry in Milan contributed to this report.