U.S. Health and Human Services Secretary Sylvia Burwell said on Wednesday that no cases of the Zika virus had been passed by mosquitoes to people in the continental United States, according to Reuters. In testimony to the House Ways and Means Committee about her department's budget request, Burwell said cases of the virus had occurred in travelers returning to the United States, and that there had been one case of sexual transmission in Dallas. The virus has been passed from mosquitoes to people in the U.S. territory of Puerto Rico, she said. President Obama is asking Congress for over $1.8 billion in emergency funds to fight Zika at home and abroad, and pursue a vaccine.