An antibody (orange) bound to the surface spike protein of SARS-CoV-2 can block infection. By Jon CohenScience’s COVID-19 reporting is supported by the Pulitzer Center.One of the first people to be diagnosed with COVID-19 in the United States hopes a legacy of her nightmare—the antibodies it left in her blood—will lead to a drug that can help others infected with the novel coronavirus that has now killed more than 250,000 people worldwide.Early this year, the woman had just learned of the outbreak in Wuhan, China, when she flew to Beijing to celebrate the Lunar New Year with her elderly parents and extended family.