Scientists have recreated the 1918 Spanish flu virus, one of the deadliest ever to emerge, to the alarm of many researchers who fear it presents a serious security risk.
Undisclosed quantities of the virus are being held in a high-security government laboratory in Atlanta, Georgia, after a nine-year effort to rebuild the agent that swept the globe in record time and claimed the lives of an estimated 50 million people.
The genetic sequence is also being made available to scientists online, a move which some fear adds a further risk of the virus being created in other labs.
The recreation was carried out in an attempt to understand what made the 1918 outbreak so devastating. Reporting in the journal Science, a team lead by Dr Jeffery Taubenberger at the Armed Forces Institute of Pathology in Maryland shows that the recreated virus is extremely effective. When injected into mice, it quickly took hold and they started to lose weight rapidly, shedding 13% of their original weight in just two days. Within six days, all mice injected with the virus had died.