http://www.nytimes.com/2012/07/31/s...ied-for-human-threat.html?partner=rss&emc=rss Excerpts: Four times in the past century, a new strain of flu has emerged that can spread quickly in humans. One of those strains, which emerged in 1918, killed an estimated 50 million people. All human flu strains evolved from flu viruses that live in birds. To understand how these transitions happen, scientists have recently been tinkering with a strain of bird flu to see how many mutations it takes until its spreads from mammal to mammal. When news of their efforts emerged last fall, a fierce debate broke out about the wisdom of publishing the experiments in full. …… Scientists may respect moratoriums, but nature does not. Evolution recently carried out an influenza experiment of its own on the coast of New England. Last fall, 162 dead harbor seal pups washed up on the beaches of New Hampshire and Massachusetts. …….. Dr. Holmes believes the new virus needs to be carefully monitored to see what sort of threat, if any, it poses. “The question mark is what it means for seals, and what it means for us,” he said. ……… In September 2011, beachgoers noticed dead seal pups on New Hampshire beaches. “Surfers were surfing into seals floating in the water,” said Katie Pugliares, a senior biologist with the New England Aquarium’s rescue program. Unlike typical seal cadavers, the seals were not malnourished, suggesting they had died suddenly. …… A new strain that can spread among seals is a reason for serious concern, Dr. Anthony said. “What we fear is that it would allow the virus to persist within the seal population,” he said. “And if it persists, who knows what other changes may accumulate over time?” “If it adapts better to mammal hosts, it may well start to move into humans,” Dr. Lipkin said. “This is clearly a virus for which we need some surveillance.” Pigs, Dr. Lipkin noted, are especially good at producing new flu strains because they can be infected by bird flu and mammal flu at the same time. Two kinds of virus can combine, giving rise to new hybrid strains. Dr. Lipkin and his colleagues found evidence that seal cells can also be invaded by both kinds of viruses — raising the possibility that they could produce new hybrid flu strains as well.