Flu virus reassortants could pose pandemic threat

Chinese researchers testing reassortants combining the 2009 H1N1 virus and the H9N2 have virus found that several were more pathogenic than the parent viruses themselves and that they could pose a pandemic threat.

H9N2 is a subtype that circulates commonly in birds, though it has also been found in pigs, which could lead to a mixing between animal and human flu viruses, CIDRAP News reports. There have been some reports of human infections with H9N2 and it has been included next to H5N1 as an annual recommendation for a pandemic flu vaccine candidate viruse by the World Health Organization.

The study found that 57.5 percent of the 127 reassortants between the two viruses had a high ability to replicate, which suggests that the viruses have high genetic compatibility. Eight of the reassortants caused more severe disease in lab mice, including symptoms like ruffled coats, dyspnea, lethargy and microscopic signs in lung tissue, like interstitial pneumonia and bronchopneumonia, CIDRAP News reports.

While the more virulent reassortants are a major concern, less pathogenic strains could circulate undetected in mammals and mutate into future pandemic threats.

The investigation concluded that these reassortants between H9N2 and pandemic H1N1 could lead to a public health threat and that the polymerase acid was the gene segment found in the most virulent strains. The PA gene could work well as a marker for identifying H9 reassortants that have the highest risk.