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

Multimedia Obama, Modi Break Nuclear Deal Deadlock

Impasse over liability issues had been stalling bilateral civilian nuclear cooperation; deal reached at start of US president's three-day visit to India More

WHO's Late Efforts in Tackling Ebola Highlight Need for Reform

Health experts debate measures to reform agency’s response to global public health emergencies in special one-day session on deadly outbreak More

One Tumultuous Year in Power for CAR's President

As sectarian violence raged across Central African Republic, interim President Catherine Samba-Panza has Herculean task: to end civil war and put country back on right track More

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Worldwide Photo Workshops Empower Youthi
X
Julie Taboh
January 23, 2015 11:08 PM
Last September, 20 young adults from South Sudan took part in a National Geographic Photo Camp. They are among hundreds of students from around the world who have learned how to use a camera to tell the stories of the people in their communities through the powerful medium of photography. Three camp participants talked about their experiences recently on a visit to Washington. VOA’s Julie Taboh reports.
Video

Video Worldwide Photo Workshops Empower Youth

Last September, 20 young adults from South Sudan took part in a National Geographic Photo Camp. They are among hundreds of students from around the world who have learned how to use a camera to tell the stories of the people in their communities through the powerful medium of photography. Three camp participants talked about their experiences recently on a visit to Washington. VOA’s Julie Taboh reports.
Video

Video US, Japan Offer Lessons as Eurozone Launches Huge Stimulus

The Euro currency has fallen sharply after the European Central Bank announced a bigger-than-expected $67 billion-a-month quantitative easing program Thursday - commonly seen as a form of printing new money. Henry Ridgwell reports for VOA from London on whether the move might rescue the eurozone economy -- and what lessons have been learned from similar programs around the world.
Video

Video Nigerian Elections Pose Concern of Potential Conflict in 'Middle Belt'

Nigeria’s north-central state of Kaduna has long been the site of fighting between Muslims and Christians as well as between people of different ethnic groups. As the February elections approach, community and religious leaders are making plans they hope will keep the streets calm after results are announced. Chris Stein reports from the state capital, Kaduna.
Video

Video As Viewership Drops, Obama Puts His Message on YouTube

Ratings reports show President Obama’s State of the Union address this week drew the lowest number of viewers for this annual speech in 15 years. White House officials anticipated this, and the president has decided to take a non-traditional approach to getting his message out. VOA White House correspondent Luis Ramirez reports.
Video

Video S. Korean Businesses Want to End Trade Restrictions With North

Business leaders in South Korea are calling for President Park Geun-hye to ease trade restrictions with North Korea that were put in place in 2010 after the sinking of a South Korean warship.Pro-business groups argue that expanding trade and investment is not only good for business, it is also good for long-term regional peace and security. VOA’s Brian Padden reports.
Video

Video US Marching Bands Grow Into a Show of Their Own

The 2014 Super Bowl halftime show was the most-watched in history - attracting an estimated 115 million viewers. That event featured pop star Bruno Mars. But the halftime show tradition started with marching bands, which still dominate the entertainment at U.S. high school and college American football games. But as Enming Liu reports in this story narrated by Adrianna Zhang, marching bands have grown into a show of their own.
Video

Video Secular, Religious Kurds Face Off in Southeast Turkey

Turkey’s predominantly Kurdish southeast has been rocked by violence between religious and secular Kurds. Dorian Jones reports on the reasons behind the stand-off from the region's main city of Diyarbakir, which suffered the bloodiest fighting.
Video

Video Kenya: Misuse of Antibiotics Leading to Resistance by Immune System

In Kenya, the rise of drug resistant bacteria could reverse the gains made by medical science over diseases that were once treatable. Kenyans could be at risk of fatalities as a result if the power in antibiotics is not preserved. Lenny Ruvaga has more on the story from Nairobi.
Video

Video Solar-Powered Plane Getting Ready to Circumnavigate Globe

Pilots of the solar plane that already set records flying without a drop of fuel are close to making their first attempt to fly the craft around the globe. They plan to do it in 25 flying days over a five month period. VOA’s George Putic reports.
Video

Video How Experts Decide Ethiopia Has the Best Coffee

Ethiopia’s coffee has been ranked as the best in the world by an international group of coffee connoisseurs. Not surprisingly, coffee is a top export for the country. But at home it is a source of pride. Marthe van der Wolf in Addis Ababa decided to find out what makes the bean and brew so special and how experts make their determinations.
Video

Video Yazidi Refugees at Center of Political Fight Between Turkey, Kurds

The treatment of thousands of Yazidis refugees who fled to Turkey to escape attacks by Islamic State militants has become the center of a dispute between the Turkish government and the country's pro-Kurdish movement. VOA's Dorian Jones reports.
Video

Video World’s Richest 1% Forecast to Own More Than Half of Global Wealth

The combined wealth of the world's richest 1 percent will overtake that of the remaining 99 percent at some point in 2016, according to the anti-poverty charity Oxfam. Campaigners are demanding that policymakers take action to address the widening gap between the ‘haves’ and the ‘have nots’, as Henry Ridgwell reports for VOA from London.

Circumventing Censorship

An Internet Primer for Healthy Web Habits

As surveillance and censoring technologies advance, so, too, do new tools for your computer or mobile device that help protect your privacy and break through Internet censorship.
More

All About America

AppleAndroid