لخّصلي

One of the greatest achievements of 20th - century medicine was the global eradication of smallpox . The disease is one of the most devastating known to mankind In 1967 , it was estimated by the World Health Organization ( WHO ) that two million people died of smallpox that year Smallpox is caused by the variola virus and is most often transmitted by inhaling the virus . It has an incubation period of between 7 and 17 days after which symptoms begin to appear . The initial symptoms are flu - like . A significant feature of the disease is the development of blisters on the upper part of the body , which eventually scab over and leave scars when the scabs fall off . Around 30 per cent of those infected with smallpox die , usually within two weeks of symptoms appearing . The first attempts to control the disease used a technique known as variolation . Dried scab tissue from victims of smallpox was used to deliberately infect young people . Of those infected by variolation , one per cent died , far fewer than the 30 per cent killed by infection in the normal way . Despite the risks , variolation was still used in some remote communities until relatively recently . However , it was the discovery of vaccination by Edward Jenner in 1796 which marked a major step forward in controlling the disease . Vaccination involves the administration of a preparation that allows the body to develop resistance to a disease without having to be exposed to it . By infecting children with cowpox , a relatively minor disease , Jenner found they developed immunity to smallpox By 1853 , infants in the UK were required by law to be vaccinated against smallpox , though the vaccines used were not always effective Cloppe Further advances were made in the 1920s with development of dried vaccines in France and the Netherlands . These were more effective but were difficult to store in hot climates . An outbreak of smallpox in New York City in 1947 led to the development of a freeze - drying technique which meant the vaccine could be stored for months without refrigeration , even in tropical climates . In 1966 , the WHO set a ten - year goal for the eradication of smallpox worldwide . Considerable resources were devoted to the development of mechanisms for reporting and monitoring the disease Improved technology and better vaccines also helped By 1980 , the WHO could formally declare smallpox eradicated worldwide . The last naturally occurring case was reported in 1977 in Somalia . The last fatality was in the UK in 1978 , following the escape of the virus from a research lab . It was the first time a human infectious disease had been completely eradicated . Smallpox was no longer a killer of humanity . Smallpox has a number of unique characteristics which made its eradication possible . Its symptoms develop quickly , making those infected aware of the disease at an early stage and reducing the possibility them unknowingly transmitting the disease to others . Because it is almost completely specific to humans , there is a very low possibility of smallpox being kept alive in animals to reinfect humans . The availability of effective vaccines was also a necessary factor . Finally , the high level of mortality from the disease made it easier to achieve global agreement on its eradication . Although smallpox has ceased to kill , it remains a potential danger to humanity . Though the possibility of the virus surviving in animals is very low , it is still a possibility . So , too , is the accidental release of material traditionally used for variolation in remote communities . However , the most pressing fear is that stocks of the variola virus set aside for research purposes could some day be used as a biological warfare agent . The proposal , in 2003 , to inoculate health care staff in some countries against such a possibility shows that the potential of smallpox to kill remains as strong as ever .