A virus that infects camels, and which is a member of the orthopox genus of poxviruses. This genus includes variola, the virus in humans that causes smallpox, and camelpox appears to be the closest relative of variola.
Humans are not infected by camelpox, but some scientists fear that this is only because people exposed to camels are almost always exposed in early years, giving them immunity. Now that people are no longer immunized against any orthopox, there might be a niche in humans for camelpox to evolve to exploit.
This is the basis of a claim made by Iraq in 1995 to weapons inspectors that it was working on weaponizing camelpox. People in Arab countries would be likely to have immunity against it, while outsiders would be more vulnerable. Since camelpox has never been known to cross to humans, the inspectors thought this was unlikely to be a serious threat; they were more afraid that Iraq was handling it as a practice for smallpox weapons.
The central part of the genome of orthopoxes is highly conserved: it codes for replication and structure. The stretches of genome on either side of the centre code for things that vary between host species, such as infectiousness. Recent research has shown that camelpox and variola are very similar even in these terminal regions, so in mass production of camelpox it could be easy for a human-infectious form to arise.
http://www.nal.usda.gov/ttic/tektran/data/000013/02/0000130251.html
New Scientist No 2339, 20 April 2002; story available on-line at http://uk.news.yahoo.com/020418/12/cx2gv.html