Smallpox was an infection that was caused by the virus called variola virus. For thousands of years, smallpox created severe illness and caused the death of hundreds of thousands of people. When it was introduced into the Americas from Europe in the 1500s, it killed many of the native populations. As late as the 1800s it was still causing the deaths of thousands when introduced into susceptible populations, such as in Hawaii, by European explorers. Fortunately, this virus was eliminated as a natural cause of disease in 1977 through effective use of vaccination programs. It is the only disease ever to be deliberately removed from the human population.
It is thought, however, that this virus could be reintroduced as an agent of biological warfare. This is because the virus is very contagious (can be spread from person to person) and can cause serious illness, even death, if an individual is not vaccinated within four days of being exposed to the virus. Since antibiotics only work against bacteria, not viruses, they are ineffective against the smallpox virus. There is no known cure.
Prior to 1972, vaccination against smallpox was standard procedure. Since that time, general vaccination against smallpox has not been recommended and therefore has been unavailable to the general population. It is thought that protection gained from the vaccination against smallpox lasts a maximum of 10 years. It is believed that few people in North America currently have protection against this disease. In light of current terrorist activity, the American and Canadian governments have acquired their own emergency supply of smallpox vaccine. These vaccinations would be used to vaccinate any people exposed to the smallpox virus should this become necessary.