News / Health

Gene Swapping Makes New China Bird Flu a Moving Target

A girl, who was previously infected with the H7N9 bird flu virus, waves as she is being transferred to a public ward from the ICU at Ditan hospital in Beijing, Apr. 15, 2013.A girl, who was previously infected with the H7N9 bird flu virus, waves as she is being transferred to a public ward from the ICU at Ditan hospital in Beijing, Apr. 15, 2013.
x
A girl, who was previously infected with the H7N9 bird flu virus, waves as she is being transferred to a public ward from the ICU at Ditan hospital in Beijing, Apr. 15, 2013.
A girl, who was previously infected with the H7N9 bird flu virus, waves as she is being transferred to a public ward from the ICU at Ditan hospital in Beijing, Apr. 15, 2013.
Reuters
A new bird flu virus that has killed 13 people in China is still evolving, making it hard for scientists to predict how dangerous it might become.
 
Influenza experts say the H7N9 strain is probably still swapping genes with other strains, seeking to select ones that might make it fitter.

If it succeeds, the world could be facing the threat of a deadly flu pandemic. But it may also fail and just fizzle out.
 
The virus' instability also raises questions about whether H7N9 might become resistant to antiviral drugs such as Roche's antiviral drug Tamiflu, a possibility already suggested by analyses of genetic data available on the strain so far.
 
“Even with just the three [gene] sequences we have available, there's some evidence that one doesn't quite fit with the other two. So we might think this virus is still fishing around for a genetic constellation that its happy with,” said Wendy Barclay, a flu virologist at Imperial College London.
 
“Maybe there are other viruses out there that it is still exchanging genes with until it gets to a stable constellation.”
 
To be able to say with any confidence whether this new strain, which before March had never been seen in humans, could go on to cause a pandemic, scientists need to know a lot more.
 
H7N9 a triple mix bird flu
 
So far, genetic sequence data from samples from three H7N9 victims and posted on the website of GISAID, the Global Initiative on Sharing All Influenza Data, show the strain is a so-called “triple reassortant” virus with a mixture of genes from three other flu strains found in birds in Asia.
 
Writing in the New England Journal of Medicine last week, researchers who conducted a detailed analysis of the strain's origin said it seemed that so far the re-assortment of genes to make H7N9 had taken place in birds rather than in humans or in any other mammal - a somewhat reassuring sign.
 
Barclay said this may continue, and could mean it is some time before the strain finds a form in which it can spread swiftly and efficiently in bird populations.
 
Yet genetic analyses also show the virus has already acquired some mutations that make it more likely be able to spread between mammals, and more able to spark a human pandemic.
 
A study in the online journal Eurosurveillance by leading flu experts Yoshihiro Kawaoka of the University of Wisconsin and Masato Tashiro at the National Institute of Infectious Diseases in Tokyo, said the H7N9 sequences “possess several characteristic features of mammalian influenza viruses, which are likely to contribute to their ability to infect humans”.
 
These features, the scientists wrote, “raise concerns regarding their pandemic potential”.
 
That sentiment was echoed on Saturday by the World Health Organization (WHO), which said “genetic changes seen among these H7N9 viruses suggesting adaptation to mammals are of concern” and warned: “Further adaptation may occur”.
 
Pandemic potential

While experts take some comfort in the lack of evidence so far that H7N9 is passing from person to person - a factor that would dramatically increase its pandemic potential - they are find little comfort in not yet knowing how the 60 or so people confirmed as having this flu strain became infected.
 
“We know H7 viruses can spill over into humans ... and for me the most important thing to find out now is from which species do we think this H7N9 is spilling over,” said An Osterhaus, head of viroscience of the Erasmus Medical Centre in the Netherlands.
 
“Is it one species? Are there different species? At this stage we are still lacking a lot of data.”
 
He said rigorous surveillance of wild birds, such as ducks and quail, and poultry such as chickens, as well as well-known flu-carrying mammals such as pigs, should yield answers.
          
Recent pandemic viruses - including the H1N1 “swine flu” of 2009/2010 - have been mammal and bird flu mixtures. Experts say these hybrids are more likely to be milder, because mammalian flu tends to make humans less severely ill than bird flu.
 
Pure bird flu strains - like the new H7N9 strain and like the H5N1 strain that has killed around 371 of 622 the people it has infected since 2003 - are generally more deadly for people.
 
The world's worst known pandemic, the “Spanish flu” of 1918 that killed more than 50 million people, was a bird flu that had picked up gene mutations that enabled it to spread efficiently in humans.
 
David Heymann, a flu expert and head of Britain's Chatham House Centre on Global Health Security, said it is important to put the discovery of H7N9 in humans into the context of modern-day scientific capability.
          
He said that in the years since the outbreak of Severe Acute Respiratory Syndrome (SARS) in China in 2003, there has been a significantly increased focus on detecting and reporting flu-like respiratory infections in Asia and across the world.
 
The harder scientists look, he said, the more likely they are to find viruses that are potentially threatening but may equally be the sort of events that in the past might have flared up and petered out again under the flu surveillance radar.
 
That said, he stressed this is no time to relax.
 
“Influenza viruses are very unstable. And [any] mutation is  a random event - so nobody can predict when it will happen,” he said. “You can't take your eye off anything. You have to keep you eye on everything.”

You May Like

Arab League Delays Forming Joint Force

Delay grows out of one of original obstacles facing pan-Arab force, analysts say: 'They may agree on the principle, but they continue to argue about how to implement the project' More

Pakistan Demands Afghanistan Protect Its Kabul Mission, Staff

Officials in Islamabad say Afghan agents are harassing Pakistani embassy personnel, particularly those living outside of mission’s compound More

US Survey: Trump Lead Grows in Republican Presidential Contest

Quinnipiac University poll shows brash billionaire real estate mogul with 28 percent support among Republican voters More

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Colombians Flee Venezuela as Border Crisis Escalatesi
X
August 27, 2015 2:08 AM
Hundreds of Colombians have fled Venezuela since last week, amid an escalating border crisis between the two countries. Last week, Venezuelan President Nicolas Maduro ordered the closure of a key border crossing after smugglers injured three Venezuelan soldiers and a civilian. The president also ordered the deportation of Colombians who are in Venezuela illegally. Zlatica Hoke reports.
Video

Video Colombians Flee Venezuela as Border Crisis Escalates

Hundreds of Colombians have fled Venezuela since last week, amid an escalating border crisis between the two countries. Last week, Venezuelan President Nicolas Maduro ordered the closure of a key border crossing after smugglers injured three Venezuelan soldiers and a civilian. The president also ordered the deportation of Colombians who are in Venezuela illegally. Zlatica Hoke reports.
Video

Video Is China's Economic Data Accurate?

Some investors say China's wild stock market gyrations have been made worse by worries about the reliability of that nation's economic data. And some critics say the reports can mislead investors by painting an unrealistically-strong picture of the economy. A key China scholar says Beijing is not fudging ((manipulating)) the numbers, but that the economy is evolving quickly from smoke-stack industries to services, and the ways of tracking new economic activity are falling behind the change. V
Video

Video Next to Iran, Climate at Forefront of Obama Agenda

President Barack Obama this week announced new initiatives aimed at making it easier for Americans to access renewable energy sources such as solar and wind. Obama is not slowing down when it comes to pushing through climate change measures, an issue he says is the greatest threat to the country’s national security. VOA correspondent Aru Pande has more from the White House.
Video

Video Shipping Containers Provide Experimental Housing

Housing prices around the San Francisco Bay area are out of reach for many people, so some young entrepreneurs, artists and tech industry workers are creating their own houses using converted shipping containers. But as VOA's Mike O’Sullivan reports from Oakland, the effort requires ingenuity and dealing with restrictive local laws.
Video

Video Arctic Draws International Competition for Oil

A new geopolitical “Great Game” is underway in earth’s northernmost region, the Arctic, where Russia has claimed a large area for resource development and President Barack Obama recently approved Shell Oil Company’s test-drilling project in an area under U.S. control. Greg Flakus reports.
Video

Video Philippine Maritime Police: Chinese Fishermen a Threat to Country’s Security

China and the Philippines both claim maritime rights in the South China Sea.  That includes the right to fish in those waters. Jason Strother reports on how the Philippines is catching Chinese nationals it says are illegal poachers. He has the story from Palawan province.
Video

Video Technique May Eliminate Drill-and-Fill Dental Care

Many people dread visiting dentists because they're afraid of drills. Now, however, a technology developed by a British firm promises to eliminate the need for mechanical cleaning of dental cavities by speeding a natural process of tooth repair. VOA’s George Putic reports.
Video

Video China's Spratly Island Building Said to Light Up the Night 'Like A City'

Southeast Asian countries claim China has illegally seized territory in the Spratly islands. It is especially a concern for a Philippine mayor who says Beijing is occupying parts of his municipality. Jason Strother reports from the capital of Palawan province, Puerto Princesa.
Video

Video Ages-old Ice Reveals Secrets of Climate Change

Ice caps don't just exist at the world's poles. There are also tropical ice caps, and the largest sits atop the Peruvian Andes - but it is melting, quickly, and may be gone within the next 20 years. George Putic reports scientists are now rushing to take samples to get at the valuable information about climate change locked in the ice.
Video

Video French Experiment in Integrating Roma Under Threat

Plans to destroy France’s oldest slum have sparked an outcry on the part of its Roma residents. As Lisa Bryant reports from the Paris suburb of La Courneuve, rights groups argue the community is a fledgling experiment on integrating Roma who are often outcasts in many parts of Europe.
Video

Video Kenyans Turn to Agriculture for Business

Each year Kenyan universities continue to churn out graduates for the job market despite the already existing high rate of unemployment among youth in the country. Some of these young men and women have realized that agriculture can be as rewarding as any other business or job, and they are resorting to agribusiness in large numbers as a way of tackling unemployment. Rael Ombuor reports for VOA.
Video

Video First Women Graduate Elite Army Ranger School

Two women are making history for the U.S. Army by proving they are among the toughest of the tough. VOA's Carla Babb reports from Fort Benning, Georgia as 94 men and those two women rise as graduates of the difficult Ranger school.

VOA Blogs