Smallpox

Definition and History of Smallpox

Smallpox is a viral disease caused by the variola virus, a member of the family poxviruses. The disease is strictly transmitted from human to human—no animal reservoir is known for smallpox. Infected persons show no symptoms for seven to 17 days, which is the usual incubation period. During this period, the infected person cannot transmit the disease to others. This period is followed by symptoms of the disease, the most important of which is fever, which is followed by a rash two or three days later. During this stage, the ill person becomes highly infective to others. Transmission of the virus occurs mainly through the respiratory route by infected droplets, or aerosols, from ill persons. Transmission through infected materials, such as bedsheets or blankets, is possible but to a lesser extent than face-to-face transmission. An ill person can be considered noninfective only after the falling of the last scab off the body.

Severity of symptoms differs among persons, depending on many factors like previous immunity to the disease. Two main types of clinical presentation of the disease are known: Variola major and Variola minor. Other forms may present but are less likely. The origin of the smallpox virus can be traced back in history. Its bad reputation as a devastating disease is the result of its fatal consequences on the affected population. It has killed millions throughout history, and nothing could be done for ill persons or their contacts until Edward Jenner developed a vaccine in 1798.

In 1967 the World Health Organization (WHO) started an intensified eradication program to eliminate smallpox from the world. In 1977, the last naturally occurring case was reported in Somalia. In 1979, the WHO confirmed the global eradication of smallpox, and in 1980 the WHO declared officially the eradication of smallpox.

The smallpox virus is kept in only two WHO collaborating centers in the world: one in the United States and one in the Russian Federation. It could not be confirmed whether there is any other stock kept illegally in other parts of the world. Keeping the WHO stock is mandatory for research purposes. Destruction of other stockpiles of the virus came in response to the international fear of using variola virus in illegal acts like bioterrorism. However, there is still fear of creating the virus through advanced biological techniques.

Significance of Smallpox

Smallpox is included in the core list of the Australian Group (an informal group of states aiming at impeding the spread of biological and chemical weapons) and the Centers for Disease Control and Prevention (CDC) list of agents that pose a threat to public health.

This enlistment is supported by some factors that make preparedness for smallpox a worthwhile activity. These factors rely mainly on the historical picture of this devastating disease that has killed millions throughout history, the high infectivity of the virus, and the current lack of immunity to the disease by most individuals all over the world. Besides, all the information known to date about the disease has been extracted mainly from studying periods in which universal immunity to the disease existed. Therefore, it is expected that if the disease emerges, it will be more virulent, and consequences of its spread could not be estimated on a confirmed basis. Also, the spread of decreased immunity as a result of various diseases, especially AIDS, makes more persons vulnerable to dangerous complications of such a disease in case it appears again.

...