The work has not stopped there. The cowpox virus, which infects a range of animals including humans, has been genetically altered in a similar way. The new virus, which is about to be tested on animals, should be lethal only to mice, Mark Buller of the University of St Louis told New Scientist. He says his work is necessary to explore what bioterrorists might do.

But the research brings closer the prospect of pox viruses that cause only mild infections in humans being turned into diseases lethal even to people who have been vaccinated. And vaccines are currently our main defence against smallpox and its relatives, such as the monkeypox that reached the US this year. Some researchers think the latest research is risky and unnecessary. "I have great concern about doing this in a pox virus that can cross species," said Ian Ramshaw of the Australian National University in Canberra on being told of Buller's work.

Ramshaw was a member of the team that accidentally discovered how to make mousepox more deadly (New Scientist, 13 January 2001, p 4). But the modified mousepox his team created was not as deadly as Buller's.

Since then, Ramshaw told New Scientist, his team has also created more deadly forms of mousepox, and has used the same method to engineer a more deadly rabbitpox virus. But this research revealed that the modified pox viruses are not contagious, he says. That is good news in the sense that these viruses could not cause ecological havoc by wiping out mouse or rabbit populations around the world if they escaped from a lab.

However, this discovery also means some bioterrorists might be more tempted to use the same trick to modify a pox virus
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Contact: Claire Bowles
claire.bowles@rbi.co.uk
44-207-331- 2751
New Scientist
29-Oct-2003