Anyone in the U.S. who thought they had the virus in December or early January probably had the flu, public health researchers said.

Experts say the idea that the virus somehow escaped the lab before spreading to over 3 million people worldwide — or, worse, that it was man-made in that lab — is "ridiculous," "foolish" and "implausible."

Yuan Zhiming, professor at WIV and the director of its National Biosafety Laboratory, said "malicious" claims about the lab had been "pulled out of thin air" and contradicted all available evidence.