Bhutan’s success in avoiding coronavirus is almost unrivalled but a rare patient death – just the kingdom’s fourth – shows more work was needed to fight the pandemic there, its leader says.The remote Himalayan nation of around 800,000 people, sandwiched between China and India, has recorded fewer Covid-19 fatalities than almost anywhere else in the world.The only places with lower official tolls are a small handful of remote Pacific islands and countries that do not publish coronavirus data,…