New bird flu scare
A spate of bird flu cases since the beginning of the year in China has experts watching closely as millions of people and poultry are on the move ahead of the Lunar New Year holiday, the world's largest annual human migration.
China has reported more than 50 H7N9 infections in 2014 after the strain jumped from birds to people for the first time last year.
The virus remains hard to catch and most cases have been linked to contact with poultry, but scientists worry that could change if it mutates into a form that allows it to spread easily among people.
For those who track influenza, the holiday, which begins January 31, is always worrying because it comes during the winter months when flu typically rages.