SAN FRANCISCO — First, there were conspiratorial whispers on social media that the coronavirus had been cooked up in a secret government lab in China. Then there were bogus medicines: gels, liquids and powders that immunized against the virus.

And then there were the false claims about governments and celebrities and racial unrest. Taiwan was covering up virus deaths, and the illness was spiraling out of control. Bill Gates, the Microsoft co-founder who now runs a philanthropic organization, was behind the spread of the virus. Italians were marching in the streets, accusing Chinese people of bringing the illness to their country. None of it was true.

As the coronavirus has spread across the world, so too has misinformation about it, despite an aggressive effort by social media companies to prevent its dissemination. Facebook, Google and Twitter said they were removing misinformation about the coronavirus as fast as they could find it, and were working with the World Health Organization and other government organizations to ensure that people got accurate information.

But a search by The New York Times found dozens of videos, photographs and written posts on each of the social media platforms that appeared to have slipped through the cracks. The posts were not limited to English. Many were originally in languages ranging from Hindi and Urdu to Hebrew and Farsi, reflecting the trajectory of the virus as it has traveled around the world.