New parrot virus linked to infections among humans, HK research finds

University of Hong Kong researchers have identified a previously unknown virus in parrots that may have helped a separate disease cross over into humans, sending six staff members at an animal quarantine centre to hospital with lung infections.

Their investigation may also shed light on why some common animal diseases suddenly become more dangerous to humans, according to the man who led the study, HKU's head of microbiology Professor Yuen Kwok-yung. The findings were published in the journal PLoS Neglected Tropical Diseases.

Yuen's team began an investigation in November 2012, when six workers at the New Territories North animal management centre in Sheung Shui became ill and were admitted to hospital with respiratory tract infections after handling parrots in quarantine.

They were later discovered to have Chlamydophila psittaci, a common virus found in 60 per cent of tropical birds but which only occasionally crosses over to humans in a small scale.

"We felt that it was unusual for Chlamydophila psittaci to have infected so many people," Yuen said. "This is why we started looking for other reasons for the disease to behave so abnormally."

The researchers studied eight of the 16 mealy parrots from South America that were being kept in the centre. They found the parrots were infected with both Chlamydophila psittaci and a virus never before identified anywhere in the world. The newly discovered virus has been named Psittacine adenovirus HKU1, after the university.

The study found that birds with a higher load of the adenovirus also carried more Chlamydia psittaci bacteria. Yuen believes the virus weakened the immune systems of the birds, allowing the production of an unusually high level of Chlamydophila psittaci - enough to cause an outbreak in humans.