The WHO “has only a limited understanding of a deadly new form of avian flu that has killed 20 people and infected more than a hundred others, a team of researchers said on Monday, leaving unclear how the disease spreads and how virulent it could become,” the Wall Street Journal reports. “The team, which is in China to study the strain of bird flu called H7N9, said they found no evidence of sustained human-to-human transmission, which could make the disease more contagious and more dangerous,” the newspaper writes, adding, “But it said it was still exploring the possibility of limited transmission via humans, given the presence of small clusters of infections.” Yang Weizhong, vice director at the Chinese Center for Disease Control and Prevention, said at a news conference on Monday, “So far, we still have limited knowledge of the virus…but we are certain that the virus is constantly changing,” according to the newspaper. The Wall Street Journal notes, “The WHO and Chinese health officials said they haven’t made a decision to develop a vaccine yet” (Fung/Chin, 4/22).