A deadly strain of avian flu may have passed between people for the first time, experts believe.The avian influenza A (H7N9) virus is thought to have been transmitted between father and daughter in eastern China, according to research published online by the British Medical Journal (BMJ). The findings provide the strongest evidence yet of H7N9 transmission between humans since its discover in February, but its ability to transmit itself was deemed "limited and non-sustainable" by the Chinese researchers behind the study.At the end of June 133 cases had been reported, including 43 deaths. Most infections have been among people visiting markets, selling live birds or among those who had contact with live poultry（家禽） in the seven to 10 days before becoming ill. The latest study examined the case of a 60-year-old father who regularly visited a live poultry market and became ill five to six days after his last visit in March. He was admitted to hospital with fever, cough and shortness of breath. Despite intensive care treatment he died of multiple organ failure on 4 May. His 32-year-old daughter, who was previously healthy, looked after him at his bedside before he was admitted to intensive care. She had no known exposure to live poultry before falling ill with a very high temperature, cough and fever. The daughter developed symptoms six days after her last contact with her father and was admitted to hospital where she died of multiple organ failure on 24 April. Follow-up investigations(调查) uncovered almost genetically identical virus strains from each patient, suggesting transmission from father to daughter. Another 43 people were also tested who had had close contact with the father, daughter or both. Dr Peter Horby, senior clinical research fellow at the Oxford University Clinical Research Unit in Hanoi, Vietnam, said of the study: "The most likely source of infection for the daughter was her father, during the period that she cared for him while he was ill. "He said “limited person to person transmission had been reported for other strains like H5N1 , H7N7, and the pig origin flu virus H3N2. Those strains had been around for more than a decade but have not progressed any further down the path towards a world-wide virus.” “Limited human-to-human transmission of H7N9 virus is therefore not surprising, but strengthening to monitor it was still needed,” Dr Horby added. 小题1:What’s the main idea of the passage ?
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