Ok. virus genomes are not static. ie they are always in a state of flux, getting bits and pieces now and then from cousin viruses from their environment. hence test kits are not 100% relaible or specific although sensitive, only testing for one part eg H1 or H5 part. the latest swine flu according to very reliable sources is a mixture of 10% type A, 10% type B and 10% swine flu like the Nipah virus in Malaysia a few years ago(which killed 20 people and the malaysian govt quickly qquarantined the whole village of nipah and killed all the pigs and that somehow stop the transmission very early in its first stage). so as long as the viral genome of bird flu H5N1(hemagglutinin peptide 1 and Neuramidase subtype 5) shares certain similar genetic codons, they can theoretically mix and combined to produce a supervirus. the virulent nature of a virus depends on infectivity, transmission, lag phase before symptoms develops(ie asymptomatic infectivity amongst the carriers-very impt as this makes a carrier more difficult to track or diagnosed before he infects others). hence an ideal super virus would therefore combine bits of material from swine flu(pigs and human share 95% same genetic material hence easier for the virus to infect humans by tagging along the nasal mucosal membranes and entering into the blood stream), type A( for infectivity and relatively long asymptomatic infective carrier state, SARs virus(for its pathogenic high infectivity and high mortality rate) and bird flu(also for its for its pathogenic high mortality rate but low infectivity potential hence by itself has not exploded on the scene yet). it just a matter of time before such virus reach the melting pot in China or mexico or india where you have an ideal natural "laboratory" ie a pig or animal farm with poor hygiene and dense human squatter development nearby and a poor health surveillance system for the "ideal" killer virus to explode. the last nearest ideal scenario happened in 2003 in China when SARS jumped from civet cats(whcih were eaten in Guangzhou) whwich harbous a SARS virus equivalent in its natural state , get mixed with part of human flu virus and jumped into human and spreads quickly throughout South east asia. why SARS was stopped short was because it does not have a long asymptomatic carrier state to elude detection, hence when patients are infective they become symptomatic/febrile and hence quickly quarantined to stop its spread. The next few years would be very dangerous as there are more migration of poor people from wastes filled villages to cities and more travelled from countries with such a pool of potent virus to other developed countries (with poor natural immunity due to lack of previous exposure). My prediction is that it would very soon before a 1918 doomsday scenario comes and it would be very , very worse.
