LONDON (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 reassortment 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 Center 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 Heyman, a flu expert and head of Britain's Chatham House Center 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 your eye on everything."

(Reporting by Kate Kelland, additional reporting by Ben Hirschler in London and Giles Elgood)

Romney used the occasion to lay out his vision of an opportunity society led by free people and free enterprises. Barack Obama, he charged, didnt believe in opportunity: When the president went after the 1 percent, he wanted only to turn the United States into one of those societies that attack success. Romneys supporters cheered.

CANBERRA (Reuters) - Australia announced a significant boost to its military air power on Friday, committing to buy up to new 100 Lockheed Martin Corp F-35 Joint Strike Fighters, as it shifts its focus back to the Indo-Pacific as China and India beef up forces.

After more than a decade of having forces first in Iraq, and then Afghanistan, Australia wants to focus on the military challenges closer to home, in line with U.S. President Barack Obama's 2011 "pivot" towards the Asia-Pacific.

In a new defense strategy, Australia reinforces that the United States remains its closest ally, but also struck a conciliatory tone towards top trading partner China, noting its rising defense capabilities are a natural outcome from its growing economy.

"The government does not approach China as an adversary. Rather, its policy is aimed at encouraging China's peaceful rise and ensuring that strategic competition in the region does not lead to conflict," the defense strategy said.

In Beijing, Chinese foreign ministry spokeswoman Hua Chunying noted Australia's assessment of China in the document "as a partner and not an opponent" and its view that the country's development was "beneficial to the region and world".

"We believe this embodies Australia's emphasis on developing China-Australia relations," she told a news briefing.

As part of Australia's military buildup, Defense Minister Stephen Smith said Canberra was committed to purchasing several squadrons of F-35s and would also buy 12 Boeing Co EA-18G electronic attack planes, modified versions of the 24 Super Hornets already equipping Australia's air force.

"This important decision will assure a first-class air combat capability for Australia through the transition period to the Joint Strike Fighter, which will proceed on its current schedule," Defense Minister Stephen Smith said.

Canberra's decision reinforces positive steps for the F-35, coming on the heels of a decision by Norway to buy six F-35s a year earlier than planned, and the Dutch parliament's decision not to reassess F-35 rivals to replace aging F-16s, despite cost overruns and development delays.

Australia's first two F-35s are due to be delivered in the United States in 2014-15. Australia will initially buy 14 F-35s, building up to three operational squadrons, of around 75 planes. The first squadron is due in service from around 2020.

The decision to stick with the F-35 will give Australia a mixed fleet of Super Hornets, Growlers and the new stealth fighters, matching the U.S. navy capability until at least 2030, Smith said.

The government also holds the option of buying a further 25 F-35s after 2030, to replace the Super Hornets when they are withdrawn from service, bringing the total of F-35s to 100.

STRATEGIC OUTLOOK

The new defense strategy is the first reassessment of Australia's military priorities since 2009, and comes after the 2011 U.S. pivot to the Asia-Pacific. Part of that pivot included U.S. marine rotations through a de-facto U.S. base in northern Australia.

The U.S. troop deployments and Australia's 2009 military strategy both upset China, particularly when Australia bluntly told China it needed to do more to explain its military plans which it said had the potential to concern its neighbors.

China has sharply increased military spending over the past three decades and its navy is now second in size only to the U.S. fleet in terms of numbers, increasing concerns from neighbors, like Japan and South Korea, involved in a series of long-running territorial disputes.

Australia's new strategy stresses the need for both China and the U.S. to build their strategic relationship, and says Australia does not believe it will have to choose between its alliance with the U.S. and its strengthening ties with China.

"Certainly there has been a lot of diplomatic varnish put on the text of this white paper, and there is nothing in there that should offend China outright," said Rory Medcalf, an analyst from the strategic policy think tank the Lowy Institute. "This white paper will certainly be one of the last steps in rebuilding Australia-China relations."

The document also stresses the growing importance of the Indian Ocean region, with India's military growth and with two thirds of global oil shipments passing through the Indian Ocean.

The strategy said the United States was likely to remain the strongest maritime power in the Indian Ocean, although China was likely to increase its presence there in the coming decades, as 80 percent of China's oil imports go through the region.

With Prime Minister Julia Gillard's minority Labor government under pressure to find budget savings to respond to collapsing revenues, Australia's net defense budget has contracted to around 1.56 percent of GDP, or A$24.2 billion. As a percentage, spending is at the lowest level since 1938.

The new white paper makes no commitments on defense spending, but says the government remains committed to a target to increase defense funding to 2.0 percent of GDP when the economic circumstances allow.

(Additional reporting by Rob Taylor and Michael Martina in BEIJING; Editing by Paul Tait, Michael Perry and Ron Popeski)

The case, combining two brought by Amazon and Overstock.com Inc, was decided by the New York State Court of Appeals by a vote of 4-1.

"It's unfortunate and the (U.S.) Supreme Court ought to look at this," Overstock acting Chief Executive Jonathan Johnson told Reuters by phone.

"We have states saying different things," he said, citing a ruling by the Illinois Supreme Court that a similar tax was not permissible.

The U.S. Supreme Court typically accepts cases where lower courts issue conflicting opinions.

"The ruling by the New York Court of Appeals conflicts with both the U.S. Supreme Court's precedents and with contrary decisions by other state courts that have looked at the same issue," an Amazon spokesman said by email.

The best solution to that conflict, he said, would be passage of federal legislation currently under consideration that would allow any state to require tax collection.

New York State Commissioner of Taxation and Finance Thomas Mattox commended the court for "recognizing the logical application of existing precedent to the 21st Century economy."

Eight other states have passed legislation similar to New York's, which requires out-of-state retailers to collect sales tax even when they do not have a physical presence in the state, but do have affiliates in the state.

Retailers with a physical presence in any state must always remit sales tax on purchases made either in a store or online, but since a 1992 Supreme Court decision, Quill Corp v. North Dakota, retailers lacking a "nexus" of operation in a state have not been required to collect sales tax.

In recent years, as online sales have grown as a portion of the retail market, Amazon has agreed to begin collecting sales taxes in California, Texas, New Jersey and some other states where it has distribution facilities or plans to build them.

Richard Pomp, professor of law at the University of Connecticut and an expert on state taxes, said the decision was not a surprise, and will have less impact today than it would have before Amazon began cutting deals with states to pay taxes.

Overstock ended its affiliate network in New York in 2008 and so the ruling will not have an impact on its operations, Johnson said.

Amazon was already paying tax to the state pending the decision, according to the New York Department of Taxation.

Between the New York law's passage in 2008 and today, online-only retailers collected and remitted $500 million in sales tax on more than $6 billion in transactions, according to the New York State Department of Taxation and Finance.

The cases are Overstock.com v. New York State Department of Taxation and Finance, New York State Court of Appeals No. APL-2012-00017, and Amazon.com v. New York State Department of Taxation and Finance, New York State Court of Appeals No. APL-2012-00045.

(Reporting by Nanette Byrnes in Chapel Hill, North Carolina; Editing by Howard Goller and Leslie Gevirtz and David Gregorio)

Experts aren't sure what's behind the increase. Could it be that children are growing up in households so clean that it leaves them more sensitive to things that can trigger allergies?Or are mom and dad paying closer attention to rashes and reactions, and more likely to call it an allergy?

"We don't really have the answer," said Dr. Lara Akinbami of the Centers for Disease Control and Prevention, the senior author of the new report released Thursday.

The CDC survey suggests that about 1 in 20 U.S. children have food allergies. That's a 50 percent increase from the late 1990s. For eczema and other skin allergies, it's 1 in 8 children, an increase of 69 percent. It found no increase, however, in hay fever or other respiratory allergies.

Already familiar with the trend in food allergies are school nurses, who have grown busier with allergy-related duties, like banishing peanuts at school parties or stocking emergency allergy medicine.

Sally Schoessler started as school nurse in 1992 in New York state, and didn't encounter a child with a food allergy for a few years. But by the time she left school nursing in 2005, "there were children in the majority of classrooms" with the disorder, said Schoessler, who now works at the National Association of School Nurses in Silver Spring, Md.

Food allergies tend to be most feared; severe cases may cause anaphylactic shock or even death from eating, say, a peanut. But many food allergies are milder and something children grow out of. Skin conditions like eczema, too, can be mild and temporary.

It's been difficult getting exact numbers for children's allergies, and the new report isn't precise. It uses annual surveys of thousands of adults interviewed in person. The report compares answers from 1997-1999 to those from 2009-2011.

Parents were asked if in the previous year their child had any kind of food or digestive allergy, any eczema or skin allergy, or any kind of respiratory allergy like hay fever.

The researchers did not ask if a doctor had made the diagnosis or check medical records. So some parents may have been stating a personal opinion, and not necessarily a correct one.

"We see a lot of kids in clinic that really aren't" allergic to the foods their parents worry about, said Dr. Morton Galina, a pediatric allergist at Atlanta's Emory School of Medicine.

For example, hives are sometimes blamed on a certain food when a virus was the actual cause, he added.

But experts also said they believe there is a real and unexplained increase going on, too.

One of the more popular theories is "the hygiene hypothesis," which says that exposure to germs and parasites in early childhood somehow prevents the body from developing certain allergies.

The hypothesis argues that there is a downside to America's culture of disinfection and overuse of antibiotics. The argument has been bolstered by a range of laboratory and observational studies, including some that have found lower rates of eczema and food allergies in foreign-born children in the U.S.

There could be other explanations, though. Big cities have higher childhood allergy rates, so maybe some air pollutant is the unrecognized trigger, said Dr. Peter Lio, a Northwestern University pediatric dermatologist who specializes in eczema.

Some suspect the change has something to do with the evolution in how foods are grown and produced, like the crossbreeding of wheat or the use of antibiotics in cattle. But Lio said tests haven't supported that.

Emory's Galina said the new CDC statistics may reflect a recent "sea change" in the recommendations for when young children should first eat certain foods.

In families with a history of eczema or food allergies, parents were advised to wait for years before introducing their young children to foods tied to severe allergies, like peanuts, milks and eggs. But professional associations changed that advice a few years ago after research suggested that allergies were more likely in those kids when the foods were delayed.

The old advice "was exactly the wrong thing to do," and could have contributed to some of the increased cases, Galina said.

The CDC report also found:

Food and respiratory allergies are more common in higher-income families than the poor,

Eczema and skin allergies are most common among the poor.

More black children have the skin problems, 17 percent, compared to 12 percent of white children and about 10 percent of Hispanic children.

The mother of a 13-year-old girl, who is black, runs an eczema support group in suburban Washington, D.C. Renee Dantzler says roughly half the families in her group are African-American. Eczema is an itchy skin condition, which often occurs on the arms or behind the knees. The cause isn't always clear.

Her daughter, Jasmine, started getting rashes at 6 months and got much worse when she was 4.

"Her whole body would flare. If she ate something, you would kind of hold your breath," Dantzler said. "And she's allergic to every grass and tree God made."

Her daughter took to wearing long sleeves and pants, even in hot weather, so people wouldn't see her skin scarred and whitened in spots from scratching. She began to improve about four years ago with steroid creams and other treatments and has gradually become less self-conscious about her skin, Dantzler said.

She's now on a school track team, which means wearing shorts.

"She's the only one on the team with long socks," her mom said.

___

Online:

CDC report: http://www.cdc.gov/nchs/

With three people killed and dozens more injured, the Boston bombing has put event organizers around the world on high alert.

Those organizing the GoodLife Fitness Toronto Marathon on May 5 have already planned to discuss event security with city police. Officials preparing Brazil for the 2014 World Cup, as well as the 2016 Olympic Games, have stated thatto ensure safety at these events. And the NFL claims it willas it prepares for next year's Super Bowl.

The NHL has already announced its plans to ramp up security efforts, and it's safe to assume other leagues and events will follow suit. But do we really need more security at public sporting events?

We've hit the streets to find out what you think. Here's what you told us:

So, what do you think? Share your thoughts in the comments area below.

"On Heaven and Earth: Pope Francis on Faith, Family and the Church in the 21st Century," which was first published in Spanish in 2010, will be released in the United States and Canada on May 7, Image Books said.

The new pope, formerly Cardinal Jorge Bergoglio of Argentina, co-wrote the book with Rabbi Abraham Skorka, rector of the Latin American Rabbinical Seminary in Buenos Aires, as a series of conversations.

Their exchanges cover topics such as God, atheism, abortion, the Holocaust, same-sex marriage, fundamentalism and globalization among other topics, the publisher said.

The book is billed as offering Francis' views on his efforts to strengthen relations between faiths.

Francis, who took his name after Saint Francis of Assisi, was elected the leader of the world's 1.2 billion Roman Catholics on March 13.

He has received high marks from U.S. Catholics and the American public, according to a Reuters/Ipsos poll released on Tuesday, but many respondents said they knew little about him.

Francis has published 11 books in his native Spanish.

The Spanish-language version of the book, entitled "Sobre el Cielo y la Terra," will also be published by Vintage Espanol in the United States and Canada.

Image Books and Vintage Espanol are imprints of Random House Inc, which is owned by Germany's Bertelsmann.

(Reporting by Eric Kelsey, editing by Jill Serjeant and Cynthia Osterman)

BEIJING (Reuters) - Cyber attacks against the United States from China are eroding the country's credibility and scaring off potential foreign investors afraid of losing their intellectual property, a senior U.S. official said on Tuesday.

The sheer scale of hacking attacks from China bred mistrust in the U.S. government as well as the business community, said Robert Hormats, U.S. under secretary of state for economic growth, energy and the environment.

China has repeatedly dismissed the accusations as groundless and claims it is the victim of a vigorous cyber campaign by the United States.

"The cyber intrusions are particularly troubling because they've gotten so much visibility lately that the intensified visibility is really undermining a lot of business confidence of people who would otherwise invest here," Hormats told Reuters.

"So it's hurt Chinese interests," he said after speaking at a U.S.-China Internet industry forum. "The Chinese really need to take a look at this and decide if it's in their interest for these policies to continue."

Hormats said it was difficult to determine the precise origins of the attacks. A U.S. computer security company released a report in February in which it said much of the hacking came from China.

"It's important to have a dialogue on this, but it's also important that the dialogue be a means to an end, and the end is really ending these practices", Hormats said.

China does not abuse the Internet, and countries should not attack other countries using Internet resources, Qian Xiaoqian, China's vice minister of the State Internet Information Office, earlier told the forum.

China suffered more than 6,600 attacks by computers based overseas in January and February, he said.

"We shouldn't militarize cyberspace," he said. "Such attacks violate the rights of other countries and also moral standards."

Chinese and U.S. speakers at the forum urged dialogue to iron out differences.

"As the world's two largest economies, both dependent on the Internet, China and the U.S. must work together to address this problem, on behalf of our own citizens, our own companies, and our own institutions," U.S. Ambassador Gary Locke said.

(Reporting by Terril Yue Jones; Editing by Jonathan Standing)

There are just 1,000 individual Yangtze finless porpoises left in the wild, according to a new report. That's less than half of what a similar survey of the porpoises found six years ago.

The rapidly dwindling numbers have conservationists worried that the species could vanish from the wild as early as 2025.

"The species is moving fast toward its ," said Wang Ding, head of the expedition to count the porpoises and a professor at the Institute of Hydrobiology at the Chinese Academy of Sciences.

Yangtze finless porpoises, the only freshwater finless porpoise in the world, live mainly in theand China's Dongting and Poyang lakes. They are threatened by shrinking food resources and man-made disturbances like shipping traffic.

The expedition, which took place over 44 days last fall, comes after a similar trek along the Yangtze in 2007 failed to find any surviving , a close relative of the finless porpoise that was subsequently declared functionally extinct.

The new report showed that some finless porpoises are splintering off into relatively isolated groups, which could hurt their ability to reproduce. The scientists also noted that more of the animals seemed to be flocking to wharf and port areas, perhaps to look for food.??

"They may risk their lives for rich fish bait resources there," Wang said in a statement from the World Wildlife Fund, a conservation group involved in the report. "But busy shipping traffic close to the port areas poses a threat to the survival of finless porpoise."

Other finless porpoises seemed to be avoiding human disturbances and were spotted gathering in dense groups in waters not open to ship traffic. But that strategy could backfire in these waters, the animals risk getting caught in illegal fishing traps.

As part of their conservation recommendations, the report authors urge for a year-round fishing ban in all river dolphin reserves, and for new reserves to be established in Poyang Lake and along the Yangtze.

The report, called the 2012 Yangtze Freshwater Dolphin Survey Report, was released Thursday (March 28).

Follow Megan Gannon onandFollow us ,& . Original article on .

Broadcaster ABC said on Thursday that the April 22 episode of "Castle," which follows a crime novelist and New York police detective, will switch dates with the April 29 episode.

Series star Stana Katic said on Twitter that the move was made "out of respect" for the victims from the twin blasts near the finish line of the Boston Marathon. The bombings killed At least three people and injured 176.

Broadcaster Fox on Tuesday pulled a recent episode of animated series "Family Guy" from rebroadcast because it had an unconnected storyline of the Boston Marathon and a bombing.

ABC is owned by Walt Disney Co and Fox by News Corp.

(Reporting by Eric Kelsey; Editing by Sandra Maler)