WASHINGTON (Reuters) - The new virus that has killed as many as 177 people and spread globally is a mongrel that appears to have mixed with another hybrid virus containing swine, bird and human bits, U.S. researchers reported on Thursday. Raul Rabadan and colleagues at Columbia University in New York analyzed the published genetic sequences from the H1N1 virus that has brought the world to the brink of a pandemic. "The closest relatives to the virus we have found are swine viruses," Rabadan said in a telephone interview. "Six segments of the virus are related to swine viruses from...