Word: h5n1
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...team of scientists from the U.S., Indonesia and Japan, led by virologist Yoshihiro Kawaoka at the University of Wisconsin - Madison, combined a strain of the deadly H5N1 avian virus with strains of H3N2 human seasonal flu, creating 254 new, mutated viruses. By injecting them in lab mice, researchers found that some of the hybrid viruses were both deadly (like bird flu) and transmissible (like seasonal human flu) - the kind of genetically mutated superflu viruses that experts have been warning about for decades. (See how to prevent illness...
...reason H5N1, which first cropped up in humans in 1997, has never given rise to a pandemic is that the virus does not appear to spread easily among people. It has been transmitted between humans only in rare cases, usually among family members in close conditions. But the fear has long been that if bird flu genetically mixed with human flu - in a process called reassortment, in which two flu viruses swap genes in an infected cell - it could create a new strain that is both deadly and transmissible, as illustrated by the new PNAS study. That's how many...
...scientists from the Centers for Disease Control and Prevention generated artificially combined H5N1 and H3N2 viruses in a lab, but the resulting hybrids were all less deadly than the original bird flu strain. That led to hopes that the H5N1 virus simply lacked the ability to be a true pandemic killer and that to become more transmissible, it would necessarily have to become less dangerous...
...protein, which gave the hybrid viruses the ability to spread easily among the lab mice. Scientists think the protein may allow hybrid viruses to grow more efficiently in the lower temperatures of the upper respiratory tract, from which the virus can more easily spread to others. (The H5N1 virus tends to infect the lower respiratory tract in humans, where it can't easily get out and spread...
Nevertheless, in the real world, H5N1 has not yet mutated into a more contagious form, despite having had plenty of chances to mix with human flu viruses. That could mean bird flu will remain a dead end, infecting the occasional unlucky person but never turning into a full-blown pandemic. But the PNAS study suggests that the potential exists, and it gives health officials a surveillance target in the form of the PB2 protein in each human H5N1 infection. Global health experts must always be ready: while the 2009 H1N1 pandemic may be winding down, the next...