Scientists working in top-security labs say they have recreated pathogens from the 1918 flu pandemic, the greatest plague of the 20th century, in a bid to find out why this strain was so extraordinarily lethal.Using reverse genetic engineering, the United States team took two key genes from the 1918 virus and slotted them into human flu viruses to which lab mice were known to be immune.The two genes code for a spike-like molecule called haemagglutinin (HA), which binds to specific receptors on the surface of cells in the body, and another protein, neuraminidase (NA).The mice were injected in the nose with the recombinant viruses.Within three days, mice that had been exposed to the HA gene were mortally ill. Post-mortems showed the virus had rampaged through their lungs, producing inflammation and haemorrhaging characteristic of the symptoms induced by the 1918 outbreak.
