There is experimental evidence that it is possible to use genetic engineering to increase the lethality of preexisting pathogens, such as mousepox or anthrax, to enable them to do even more damage than they would without modifications.
It has also proved possible to resurrect viruses that have been frozen for almost a hundred years, as was done recently with the 1918 Spanish flu virus, which killed 50-100 million people worldwide in 1918-1919, more than twice the deaths of World War I, which immediately preceded the pandemic. Besides being recreated and used to infect test animals, all of which contracted severe disease and many of which died, the entire genome of the virus has been sequenced and published on the Internet for anybody to download. The wisdom of such a move was criticized by technologists Ray Kurzweil and Bill Joy in the New York Times.
"Superbug" in the context of this article refers to the possibility of an engineered biowarfare or bioterrorism agent. Another meaning for "superbug" refers to microbes that evolve exclusively in hospitals (where selection pressure for evolution is strongest) and are antibiotic-resistant. The best known antibiotic-resistant "superbug" is the staph infection and its variants. Despite the fact that neither are connected today, the possibility exists that the engineers of bioweapons could exploit antibiotic-resistant microbes for biowarfare capabilities.
According to the UN Biological Weapons Convention of 1972, all biological weapons are outlawed by use among the signatory states, which include practically every major world power. Non-signing states include the tiny republic of San Marino, Israel, Mauritania, Chad, Cameroon, Angola, Namibia, Eritrea, Comoros, and a few island nations in the Pacific. However, in the interests of Realpolitik, major powers still conduct "biodefense" research, ostensibly for the purpose of preventing attacks rather than launching them. This research has included infecting monkeys with smallpox and creating strains of anthrax so lethal they kill hamsters that are genetically resistant to the disease or have been injected with a vaccine.
Creating a superbug is probably not as complicated as its seems. In his book about smallpox and anthrax, The Demon in the Freezer, science writer Richard Preston wrote, "The main thing that stands between the human species and the creation of a supervirus is a sense of responsibility among individual biologists." Bacteria take in new genetic material very readily, a process called transformation, that makes it easy to custom-insert specific genes into bacteria to get them to produce precise chemicals. For instance, to make very pure amounts of botulinum toxin for botox therapy, scientists insert a botulinum-making gene into sterile bacteria like laboratory strains of E. coli. Botulinum toxin is the most lethal substance in the world, capable of killing with as little as 50 nanograms. If a highly virulent strain of bacteria were given the gene to synthesize botulinum toxin and the resulting superbug were released simultaneously in several major airports, the result could kill tens, thousands, or even millions -- no one knows.