Those results are significant in two ways. First, they provide an obvious starting point for anyone who might want to create and release an enhanced pox virus. Mousepox is closely related to several viruses that can cause disease in humans, including viruses that cause smallpox, cowpox, and monkeypox. It would not be difficult for a skilled scientist or technician to use the published results to carry out an analogous genetic manipulation of one of those viruses; the effect of the manipulation of the other pox viruses on virulence and on the ability to overcome vaccine in these is not known. Second, they clearly demonstrate the important principle that gene sequences in a host can be as important to people who intend to enhance a pathogen as gene sequences in the pathogen itself. In this case, replicating the work requires the human IL-4 gene sequence. It should be noted that the effect of the modification in the mousepox virus was to make the host more susceptible. That requires an understanding of the host in addition to an understanding of the virus. A number of microbial pathogens cause disease by manipulating host immune function. One important implication is that a potential bioterrorist could use human, animal, or plant genome sequences to create a more dangerous pathogen.