Experts look for clues in 1918 pandemic virus family tree

first_imgJun 29, 2009 (CIDRAP News) – To outside observers, the novel H1N1 virus spreading quickly to every corner of the globe must seem like it came out of nowhere, but the organism is a fourth generation of the 1918 pandemic virus and comes from an H1N1 family tree that is colorful and complex, according to two historical reviews that appear today in the New England Journal of Medicine (NEJM).Understanding the history of swine influenza viruses, particularly their contribution to the 1918 pandemic virus, underscores the need to better comprehend zoonotic viruses as well as the dynamics of human pandemic viruses that can arise from them, the authors report in an early online NEJM edition.The world is still in a “pandemic era” that began in 1918, wrote three experts from the National Institute of Allergy and Infectious Diseases (NIAID), senior investigator David Morens, MD, medical epidemiologist Jeffery Taubenberger, MD, PhD, and NIAID director Anthony Fauci, MD.The 1918 virus has used a “bag of evolutionary tricks” to survive in humans and pigs and to launch other novel viruses, they wrote. “The 2009 H1N1 pandemic virus represents yet another genetic product in the still-growing family tree of this remarkable 1918 virus.”The novel H1N1 virus’ complex evolutionary history involved genetic mixing within human viruses and between avian- and swine-adapted viruses, gene segment evolution in multiple species, and evolution from the selection pressure of herd immunity in populations at different times, the group wrote, adding. “The fact that this novel H1N1 influenza A virus has become a pandemic virus expands the previous definition of the term,”Though any new virus is unpredictable, Fauci and his colleagues wrote that in this pandemic era, severity appears to be decreasing over time, with an evolutionary pattern that appears to favor transmissibility over pathogenicity.Two researchers from the University of Pittsburgh, in a review article on the emergence of H1N1 viruses, wrote that viral adaptation to a new host species is complex, but the 1918 influenza A H1N1 virus was unusual because it emerged from a bird source in pigs and humans at the same time. In contrast, researchers have said the new H1N1 virus probably emerged from swine to humans. The authors are Shanta Zimmer, MD, from the medical school, and Donald Burke, MD, from the graduate school of public health.Previous research suggests that antibody specificity against the 1918 human influenza virus diverged quickly from swine influenza viruses, and genetic differences in hemagglutinin (HA) continue to show the same type of rapid divergence between human and swine viruses, they wrote.Researchers still don’t know why H1N1 retreated in 1957 for the next 20 years, though likely factors include high levels of existing homologous immunity plus the sudden appearance of heterologous immunity from a new H2N2 strain, Zimmer and Burke wrote.Cross-species transfers of swine influenza H1N1 cropped up a few times over the next two decades, and human H1N1 didn’t surface again until 1977, presumably because of a laboratory accident in the former Soviet Union. This event marked a first in interpandemic history: the cocirculation of two influenza A viruses.The authors wrote that it’s difficult to predict how well the pandemic strain will compete against the seasonal H1N1 virus. Both viruses share three gene segments with their remote 1918 descendant: nucleocapsid, nonstructural, and HA. They pointed out that studies of B-cell memory response in 1918 pandemic survivors showed that the neutralizing body against HA was specific and long-lasting.Cell-mediated immunity may also affect competition between the two viruses, the authors wrote. Though it’s not clear if cytotoxic T lymphocytes clinically protect humans, they have been shown to reduce viral shedding, even in the absence of antibodies against HA and neuraminidase.”Cytotoxic T lymphocytes that are generated by seasonal influenza viruses against conserved epitopes might provide heterotypic immune responses that could dampen transmission, even in the absence of measurable antibody protection,” Zimmer and Burke wrote.Morens DM, Taubenberger JK, Fauci AS. The persistent legacy of the 1918 influenza virus. N Engl J Med 2009 Jul 16;361(3):225-29 [Full text]Zimmer SM, Burke DS. Historical perspective—emergence of influenza A (H1N1) viruses. N Engl J Med 2009 Jul 16;361(3):279-85 [Full text]last_img read more

Pirate treasure discovered off the coast of Madagascar

first_imgMassive Gas field discovered off the coast of Egypt More than 50 migrant bodies discovered off coast of Libya Madagascar Election 2013 Videoscenter_img A team of American explorers on Thursday claimed to have discovered silver treasure from the infamous 17th-century Scottish pirate William Kidd in a shipwreck off the coast of Madagascar.Marine archaeologist Barry Clifford told reporters he had found a 110-pound silver bar in the wreck of Kidd’s ship the “Adventure Gallery”, close to the small island of Sainte Marie.But UNESCO, the United Nations’ cultural body, immediately criticized Clifford’s methods and said he may have damaged a precious archeological site in his hunt for treasure.Captain Kidd, who was born in Scotland in about 1645, was first employed by British authorities to hunt pirates, before he himself turned into a ruthless criminal of the high seas.After looting a ship laden with valuable cargo in 1698, he was caught, imprisoned and questioned by the British parliament before being executed in Wapping, close to the River Thames, in 1701.The fate of much of his booty, however, has remained a mystery, sparking intrigue and excitement for generations of treasure-hunters.Clifford, who was filmed by a documentary crew lifting the silver ingot off the sea bed, handed it over to Madagascan President Hery Rajaonarimampianina on Sainte Marie on Thursday.Soldiers guarded the apparent treasure at the ceremony, which was attended by the U.S. and British ambassadors.“We discovered 13 ships in the bay,” Clifford said. “We’ve been working on two of them over the last 10 weeks.“One of them is the ‘Fire Dragon’, the other is Captain Kidd’s ship, the ‘Adventure Galley’.”October Films, the British production team behind the project, struck a more cautious note, saying that the silver ingot was of the correct date and appeared similar to other ingots linked to Kidd.“Further analysis of the ingot will be required to confirm these preliminary findings,” the company added.Archaeologist John de Bry, who attended the ceremony, said the shipwreck and silver bar were “irrefutable proof that this is indeed the treasure of the ‘Adventure Gallery’.”The ship, which was armed with 34 big guns, is thought to have been scuttled by Kidd during an expedition to the Indian Ocean.–AFPRelatedlast_img read more