Top American health officials who critics say misled Congress with claims regarding U.S.-funded virus research in China are pushing back after documents were released appearing to show that the United States did pay for gain-of-function research, contrary to the officials’ testimony. The National Institutes of Health (NIH) sent the documents last week to lawmakers. They show that the NIH funded research that increased the function of coronaviruses and MERS, experts said. Dr. Francis Collins, the head of the NIH, and Dr. Anthony Fauci, who heads one of the institutes, told Congress earlier this year that the agency did not fund gain-of-function research. Critics said the new documents were further proof Collins and Fauci misled Congress. “In the letter they acknowledge that yes, the viruses did gain in function, they became more dangerous. So they’ve created a virus that doesn’t exist in nature to become more dangerous, that is gain-of-function,” Sen. …