Smallpox is an infectious disease of the past that health care professionals eliminated worldwide by vaccination. The variola virus causes the disease, which only spreads from person to person. Affected people became very ill with a high fever and a characteristic rash. Up to one-third of people with smallpox died. Although the disease has been wiped out, samples of the virus still exist in high-security laboratories in the United States and Russia. This has led to concerns about use of the virus in biological warfare. For this reason, health care providers still vaccinate some military personnel against smallpox.
Smallpox existed for more than 12,000 years. Mummies from ancient Egypt showed evidence of infection, including the mummy of Ramses V. Smallpox entered the New World in the 16th century, carried by European explorers and conquistadors. Because the aboriginal inhabitants had no immunity to the disease, smallpox often decimated native populations. There are even reports where people intentionally infected Native American populations with infected blankets in the 18th century — one of the early examples of biological warfare. During the 20th century, there were 300 million to 500 million deaths from smallpox worldwide, compared to 100 million from tuberculosis.
It was not until the end of the 18th century that an effective method of vaccination was developed. An English scientist named Edward Jenner discovered it. Jenner observed that milkmaids often got a mild disease called cowpox and that this seemed to make them immune to smallpox. His vaccination strategy involved transferring the blister fluid from a person with cowpox to a person who had not yet had smallpox (an obsolete process termed variolation). This gave the susceptible person a cowpox infection (which was usually mild) and conveyed protection from smallpox. After a time, a virus similar to cowpox, called vaccinia, was substituted in the vaccine.
The last naturally occurring case of smallpox was in Somalia in 1977. In 1980, the World Health Organization (WHO) and the World Health Assembly certified that the world was finally free of smallpox. Thus, smallpox was the first disease to be entirely eradicated. Campaigns are now under way to try to eliminate other diseases such as polio and measles.
The WHO, post-eradication of the virus clinically (no smallpox cases in the world), has encouraged all member nations to destroy any remaining laboratory cultures of the virus. However, the rise of biological warfare technology led to concerns that people could weaponize smallpox to use in bioterrorism. Both the U.S. (CDC, Atlanta, Georgia) and Russia (Koltsovo) decided to retain their stockpiles in case they were needed to produce novel vaccines against a biological agent. This has understandably stirred up controversy. Supporters of retaining the cultures note that existing stocks of the virus have been used to develop and test new treatments and vaccines. The entire viral genome has been sequenced, leading to concerns that the virus may be recreated even if current stocks are destroyed.
Smallpox is a life-threatening disease (30% or higher death rate with severe hemorrhagic disease) and is on the list of potential biological weapons considered to pose the greatest threat to public health. Other agents on this list include anthrax, plague, smallpox, botulism, tularemia, and the viral hemorrhagic fevers, including Ebola and Marburg viruses
