Chiron Corp. has won a contract to develop a human vaccine against a strain of bird flu that can infect people and “has the potential to trigger a modern-day pandemic,” the U.S. government said on Tuesday.

The National Institute of Allergy and Infectious Diseases said it had awarded Chiron, of Emeryville, California, the contract to develop a vaccine against the H9N2 strain of avian influenza virus.

Avian influenza has been sweeping through poultry farms and markets across Asia this year, forcing the culls of millions of birds and devastating the industry in some areas.

Some varieties cannot infect people, but some - notably the H5N1 and H9N2 strains - have jumped to humans and can cause an especially serious and deadly disease in people.

“In 1999 and 2003, an H9N2 influenza strain caused illness in three people in Hong Kong,” the NIAID, one of the National Institutes of Health, said in a statement.

“Scientists are concerned about H9N2 and other emerging types of avian influenza viruses because as they spread - most commonly through poultry - they continually mutate, increasing chances that they may infect humans, evade the body’s immune response and become more lethal,” it added.

“Of greatest concern is that these ever-changing avian viruses could develop the ability to spread from person to person, resulting in a fast-moving, global pandemic.”

In 1918 a strain of flu that scientists now say had many bird flu characteristics swept the world, killing as many as 40 million people.

Just last week, scientists in Hong Kong sounded an alarm after finding that H9N2 was prevalent in chickens in local markets and could mutate and jump more easily to humans.

“Pandemic influenza has the potential to devastate human health right across the world, and therefore this type of public-private partnership is crucial to further our pandemic preparedness,” said John Lambert, president of Chiron Vaccines.

Under the contract, Chiron will produce up to 40,000 doses of the vaccine. NIAID will conduct the clinical studies to see if the vaccine is safe and works in people.

Chiron said it would manufacture the vaccine at its production facilities in Siena and Rosia, Italy.

Oxford, Britain-based Chiron Vaccines is the world’s second-largest maker of influenza vaccines.