<unk>  or the<unk>  fatality ratio from<unk>  or the case-fatality rate of<unk>  refer to the ratio of the number of confirmed<unk>  deaths resulting from confirmed cases of transmission and infection of<unk>  to the number of those confirmed cases. For example, if there are 100 confirmed cases of<unk> s infected with<unk>  and 10 die, then there is a 10%<unk>  fatality ratio (or<unk>  rate).<unk>  flu is a concern due to the global spread of<unk>  that constitutes a pandemic threat. The majority of<unk>  flu cases have been reported in southeast and east Asia. The case-fatality rate is central to pandemic planning. Estimates of case-fatality (CF) rates for past influenza pandemics have ranged from to 2-3% for the 1918 pandemic to about 0.6% for the 1957 pandemic to 0.2% for the 1968 pandemic. As of 2008, the official World Health Organization estimate for the case-fatality rate for the outbreak of<unk>  avian influenza was approximately 60%. Public health officials in Ontario, Canada argue that the true case-fatality rate could be lower, pointing to studies suggesting it could be 14–33%, but warned that it was unlikely to be as low as the 0.1–0.4% rate that was built into many pandemic plans.<unk>  infections in<unk> s are generally caused by bird to<unk>  transmission of the virus. Until May 2006, the WHO estimate of the number of<unk>  to<unk>  transmissions had been "two or three cases". On May 24, 2006, Dr. Julie L. Gerberding, director of the United States Centers for Disease Control and Prevention in Atlanta, estimated that there had been "at least three." On May 30, Maria Cheng, a WHO spokeswoman, said there were "probably about half a dozen," but that no one "has got a solid number." The cases of suspected<unk>  to<unk>  transmission that continue to be found have been isolated and contained, and include transmission among members of a family in Sumatra, Indonesia in June 2006 as well as earlier and later instances arising in other countries. However, no pandemic strain of<unk>  has yet been found. The key point is that, at present, "the virus is not spreading efficiently or sustainably among<unk> s."<unk>  vaccines for chickens exist and are sometimes used, although there are many difficulties that make it especially difficult to decide whether vaccination will do more harm than good. In the U.S.<unk>  pre-pandemic vaccines exist in quantities sufficient to inoculate a few million people and might be useful for priming to "boost the immune response to a different<unk>  vaccine tailor-made years later to thwart an emerging pandemic". Japan has inoculated 6,000 health care workers with a pre-pandemic vaccine, and is planning how to proceed with widespread vaccinations, particularly workers who would provide utilities during an outbreak. Switzerland is also considering preemptive vaccination to protect the general public.<unk>  pandemic vaccines and the technologies to rapidly create them are in the<unk>  clinical trials stage but cannot be verified as useful until after a pandemic strain emerges. Efforts to identify the changes that might result in a<unk> -communicable strain have resulted in laboratory-generated<unk>  with substantially greater affinity for<unk>  cellular receptors after a change of just two of the H5 surface proteins. Significantly, mouse antibodies were 10 times less potent against the mutants than against the pre-mutated viruses.
Human mortality from H5N1
Third plague pandemic
First plague pandemic
HIV/AIDS in North America
Second plague pandemic
HIV/AIDS in Europe
HIV/AIDS in Asia
Native American disease and epidemics