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Saturday, December 01, 2001


Smallpox: The Next Threat?

This is the second article in our series on bioterrorism; the first one focused on recent anthrax threats.

Future attacks on the United States and Western nations with biological or chemical weapons is an eventuality that must be actively addressed. Civilian and military public-health agencies are preparing to cope with biological and chemical warfare through efforts to stockpile vaccines and antibiotics. While new vaccines are being actively developed, other biologics are needed to counteract the effects of these weapons on the general population.

Smallpox is a particularly dangerous threat because of its clinical and epidemiological properties. The virus can be manufactured in large quantities, stored for extended periods, and delivered as an infectious aerosol. Smallpox probably was first used as a biological weapon during the French and Indian Wars (1754-1767) by British forces in North America. Soldiers distributed blankets that had been used by smallpox patients with the intent of initiating outbreaks among American Indians. Epidemics occurred, killing more than 50 percent of many infected tribes.

A global campaign was begun in 1967 by the World Health Organization (WHO) to eradicate smallpox. The last known case of smallpox occurred in Somalia in 1977, and the WHO certified in 1980 that the disease had been eradicated from the planet. With the elimination of smallpox came the recommendation that all countries stop vaccinating against the disease. The only known remaining samples of smallpox virus are held in secure facilities at the Centers for Disease Control and Prevention (CDC) in Atlanta and the Institute for Viral Preparations in Koltsovo, Russia. With the success of the WHO campaign to eradicate naturally occurring smallpox and the subsequent discontinuation of vaccination, a large proportion of the population has no immunity. Death rates could be higher than 25 percent today if smallpox were released through a biological weapon.

Although there is no proof, evidence indicating that other nations may possess the smallpox virus has led to a concern that terrorists might have acquired samples of smallpox as well. Recent allegations from Ken Alibek, a former deputy director of the Soviet Union’s civilian bioweapons program, have heightened worries that smallpox might be used as a biological weapon. Alibek reported that, beginning in 1980, the Soviet government embarked on a successful program to produce the smallpox virus in large quantities and adapt it for use in bombs and intercontinental ballistic missiles. The program had an annual industrial capacity of many tons of smallpox virus. Alibek reports that Russia even now has a research program that seeks to produce more deadly and contagious strains. Because financial support for laboratories in Russia has sharply decreased in recent years, there are increasing concerns that existing expertise and equipment might fall into non-Russian hands.

Smallpox was once worldwide in scope, and, before vaccination was practiced, almost everyone contracted the disease. Smallpox is a viral illness that occurs only in humans. During the smallpox era, about 30 percent of infected people died. Smallpox can be easily spread from person to person by aerosols, droplets from the mouth of infected persons, and direct contact. Contaminated clothing or bed linens can also spread the virus. Initially, infected persons typically experience high fever, malaise, headache, and backache. Subsequently, the typical rash of smallpox is seen and is most prominent on the face and extremities; it appears all at once in contrast to the rash from chickenpox, which develops over several days. In addition, multiple smallpox lesions are often found on the palms of the hands and the soles of the feet, which is unusual in chickenpox. Smallpox lesions are deep and often produce scars. There are no specific medications proven to cure smallpox.

Smallpox vaccine is no longer licensed or available commercially in the United States because there is no current need for its use. The US Public Health Service does maintain an emergency stockpile, however, and the federal government just signed an agreement with a drug company to produce smallpox vaccine.

The deliberate reintroduction of smallpox as an epidemic disease would be an international crime of unprecedented proportions. If used as a biological weapon, smallpox represents a serious threat to civilian populations because of its fatality rate of 30 percent or more among unvaccinated persons (which many of us and our children are today) and the absence of a specific treatment. Although smallpox has long been feared as the most devastating of all infectious diseases, its current potential for devastation is far greater than at any previous time. As routine vaccination stopped more than 25 years ago, smallpox would be able to spread rapidly throughout the world’s now highly susceptible, mobile population.

Theoklis Zaoutis is attending physician in special immunology (pediatric HIV) at the Children’s Hospital of Philadelphia and an investigator for the Pediatric AIDS Clinical Trials Group (PACTG). He is also a fellow in pediatric infectious diseases at the Children’s Hospital of Philadelphia and an instructor in the department of pediatrics at the University of Pennsylvania School of Medicine.
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