Summary Research into making bird flu easier to spread in people is to resume after a year-long pause.
Some argue the research is essential for understanding how viruses spread and could be used to prevent deadly pandemics killing millions of people.
Research was stopped amid fierce debate including concerns about modified viruses escaping the laboratory or being used for terrorism.
The moratorium gave authorities time to fully assess the safety of the studies.
A type of bird flu known as H5N1 is deadly and has killed about half the people who have been infected.
It has not caused millions of deaths around the world because it lacks the ability to spread from one person to another. Cases tend to come from close contact with infected birds.
Scientists at the Erasmus University in the Netherlands and the University of Wisconsin-Madison in the US discovered it would take between five and nine mutations in the virus genetic code to allow it to start a deadly pandemic.
