By Michael Martina and Kate Kelland BEIJING/LONDON (Reuters) - China has earned praise from international scientists for its handling of an outbreak of a deadly new bird flu in humans, but a history of public health cover-ups means the Chinese public is harder to win over. Even as global authorities have said the new H7N9 bird flu strain that has killed eight and infected 28 is no cause for panic, memories of past health scandals continue to undermine the government's credibility at home in dealing with outbreaks. ...