New bird flu strain in China has experts worried about pandemic

Lab experiments on a new strain of the H7N9 bird flu circulating in China suggest the virus can transmit easily among animals and can cause lethal disease among humans, researchers reported on Thursday, raising fears of another pandemic.

The H7N9 virus has been circulating in China since 2013, causing severe disease in people exposed to infected poultry. India has in the past been among the countries worst affected by bird flu, exacerbated by the practice of feeding antibiotics to poultry to make it grow faster.

Last year, human cases of bird flu spiked, and the virus split into two distinct strains that are so different they no longer succumb to existing vaccines. One of these has also become highly pathogenic, meaning it has the ability to kill infected birds, posing a threat to the poultry industry.

American and Japanese researchers have tested the new bird flu strain, and a report published by the researchers in Cell Host and Microbe on Thursday said the new virus strain that was tested on mice, ferrets and other non-human mammals had replicated efficiently.

Flu expert Yoshihiro Kawaoka of the University of Wisconsin and researchers tested a version of the new H7N9 strain taken from a person who died from the infection last spring.

According to the scientists' report, the virus spreads rather quickly from cage to cage, meaning the virus could get transferred to other animals via respiratory droplets through sneezing and coughing.

What's even more alarming is that two of the three healthy ferrets the scientists infected with the new strain of H7N9 virus died during the test. This could mean that even a tiny droplet containing the virus may cause severe implications.

Mammals including ferrets are considered the best animal model for testing the transmissibility of influenza in humans.

"The work is very concerning in terms of the implications for what H7N9 might do in the days ahead in terms of human infection," Michael Osterholm, an infectious disease expert from the University of Minnesota, told Reuters.

Since 2013, the H7N9 bird flu virus has sickened at least 1,562 people in China and killed at least 612. Some 40 per cent of people hospitalised with the virus die.

In the first four epidemics, the virus showed few changes. But last flu season, there were some 764 cases – nearly half of the 1,562 total.

"The whole world is worried about it," Osterholm said.

A new risk assessment tool from the US Centers for Disease Control and Prevention (CDC) ranks H7N9 as the top animal flu strain, with the potential of causing a human pandemic.

The most recent global pandemic was the 2009 H1N1 swine flu outbreak that infected millions and killed more than 200,000 globally.

Some researchers are concerned that the highly pathogenic strain could cause even more severe disease and higher death rates, but mortality from the low pathogenic strain is already "alarmingly high", said Dr Timothy Uyeki, a flu expert at the CDC.

Existing H7N9 vaccines are based on the 2013 strain. The CDC has developed a new vaccine based on the low pathogenic strain of the mutated virus, Uyeki said. The low pathogenic strain accounted for most of the human infections last year.

Uyeki believes the vaccine would likely also offer protection from the new highly pathogenic H7N9 strain, but it needs to be tested in people.

In February, China gave the go ahead for clinical trials of H7N9 vaccines developed by state-owned Beijing Tiantan Biological. The company said in a filing that it was developing four vaccines against the H7N9 virus.