By Jennifer Rigby and Josephine Mason LONDON (Reuters) -The head of the World Health Organization said on Tuesday China’s zero-tolerance COVID-19 policy is not sustainable given what is now known of the virus, in rare public comments by the U.N. agency on a government’s handling of the pandemic. “We don’t think that it is sustainable considering the behaviour of the virus and what we now anticipate in the future,” WHO Director-General Tedros Adhanom Ghebreyesus told a media briefing. “We have discussed this issue with Chinese experts. And we indicated that the approach will not be sustainable….