Sir

The Nature Science Update “Synthetic viruses just around the corner”1 reported a discussion about scientists' imminent ability to synthesize new viruses for producing better vaccines or for devising deadlier biological weapons. I would like to give an example where genetic engineering of viruses can undermine careful management of natural resources.

Two new rabbit virus strains are being developed for opposing reasons. On the one hand, a group in Australia is modifying rabbit myxoma virus to transmit reproductive sterility and so reduce numbers in a region where rabbits constitute a pest2. On the other, a European group is modifying myxoma virus to express rabbit haemorrhagic disease virus capsid protein3 to protect rabbits against both diseases and encourage the recovery of wild populations within the species' original distribution area.

Each goal is logical within its regional context. However, the history of rabbit viruses shows that outcomes can conflict with initial goals. First recorded in Montevideo in 1896, myxoma virus was successfully released in Australia in 1950 to control rabbit populations, but an illegal release in 1952 in France led to the virus spreading throughout Europe. Similarly, rabbit haemorrhagic disease, which spread naturally from Chinese rabbitries throughout Europe in 1987, spread in Australia after an accidental release from a trial island and in New Zealand after an illegal release in 1997.

The new modified viruses could spread worldwide as easily as myxomatosis and rabbit haemorrhagic disease initially spread. The establishment of modified myxoma virus into inappropriate regions could have disastrous effects on biodiversity. The preservation of Australasian ecosystems, as well as the conservation of endangered predators in Europe, depends on the same species: the wild rabbit, the target of both modified viruses.

It is therefore essential that modified viruses are very carefully and appropriately used. Biotechnology policies on the release of modified organisms rely on national authorities. But rabbits are distributed throughout the world, so it is essential to guide the development, release and regulation of rabbit virus biotechnology, and to enforce international controls to prevent accidental spread of genetically modified viruses.