Former top US health official Anthony Fauci has refused to answer questions at a tense US Senate hearing on Covid-19, saying he feared Republicans would try to use his testimony to prosecute him for perjury. Fauci noted he had testified about Covid and its origin at several congressional hearings. Republicans have long accused Fauci of concealing information about the pandemic from the public and lying about its dangers. Fauci has called the allegations against him "simply preposterous" in previous testimony to lawmakers. In his statement to the Senate Committee on Homeland Security on Wednesday, Fauci said Republican Senator Rand Paul, who chaired the hearing, had an "obvious obsession" with prosecuting him and that had led Fauci to decline to answer questions.