Smallpox: could a deadly disease—declared eradicated on Earth—come back to haunt humans as a bioweapon?

Science World, March 7, 2003 by Michael Stroh

It's one of history's oldest and most fearsome killers. Smallpox causes scorching fever, oozing blisters, terrible scarring--and death, especially in children. Thought to have taken its first human life 10,000 years ago in Africa or Asia, the earliest evidence of its deadly mischief is found on the scarred faces of mummies in the Cairo Museum.

It's also written all over the history books: Mass outbreaks of the disease gutted the world's greatest empires, from the Romans to the Aztecs, and spared neither peasants nor princes: King Louis XV of France died of it; Abraham Lincoln survived, but probably carried lasting battle scars.

Smallpox is also the only disease to be deliberately--and successfully--wiped out by man. The drive to defeat it accelerated in the 18th century, when a British doctor named Edward Jenner developed the first smallpox vaccine, a substance to shield humans against the disease.

Millions lined up for Jenner's lifesaving discovery in the centuries that followed--and slowly the number of cases began to drop. Smallpox hasn't been seen on U.S. soil since 1949, but in Africa and Asia the disease continued to ravage poor and remote regions. So in 1967, the World Health Organization (WHO) launched a global vaccination campaign to eradicate smallpox. The strategy worked--the world's last natural case occurred on October 27, 1977, in a hospital cook in Somalia.

Today, the virus (microscopic panicle) that causes smallpox officially exists in just two places: a high-security U.S. government laboratory in Atlanta and a similar lab in Russia. But in the aftermath of 9/11, some experts fear that terrorists or nations such as Iraq may have secretly acquired the virus for use as a biological weapon. To prepare for any potential threat, the U.S. government in January announced a far-reaching program to vaccinate 11 million health-care workers and military personnel. But the plan has sparked raging controversy. More than 80 U.S. hospitals are refusing to administer the vaccine, which can trigger rare but severe side effects--including death. "The cost in deaths from vaccine complications will outweigh any benefits," argues Dr. Thomas Mack, a University of Southern California smallpox expert.

Others disagree: "The threat of bioterrorism is real," stresses Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases. To show Americans they have nothing to fear, President George W. Bush rolled up his sleeve to receive his own shot last December. What exactly is this disease, and just how real is the threat? Read on.

Q: What is smallpox, and what are its symptoms?

A: Smallpox is a contagious and often-fatal disease caused by the variola virus, a particle so tiny that roughly 1,000 linked together span the width of a human hair. Despite its size, variola is a potential killing machine: Nearly one out of every three infected people die.

The disease assumes different forms. But a person infected by the virus usually feels nothing for the first seven to 17 days. Then, signs of malignant smallpox set in: high fever, chills, body aches, and vomiting--most people are too sick to get out of bed. After two to four days, a scarlet rash appears in the mouth and throat, then on the face and forearms; soon it spreads to the entire body. As the rash spreads, the fever usually breaks. The person may even start to feel better--but actually the worst is yet to come.

The rash gives way to tiny bumps, which fill up with a thick milky fluid. The fever returns and the bumps become painful pustules--dense pus-filled blisters that look like BB pellets embedded in the skin, mostly on the face, arms, and legs. By the second week, the pustules start hardening into crusty brown scabs, which fall off after three to four weeks, leaving permanent pitted scars.

"The exact cause of death in fatal smallpox is unknown to science," notes Richard Preston in his book The Demon in the Freezer. But he says physicians who have watched it know its horrors: "As the end approaches, the smallpox victim can remain conscious, in a kind of frozen awareness."

Q: How is the disease spread?

A: Smallpox passes from person to person primarily through air on virus-laden water droplets that explode from a patient's mouth when he or she coughs or sneezes. Occasionally someone can become infected by contaminated bedding, clothes, or other objects. As far as scientists know, neither insects nor animals transmit the disease. But a human infected with the disease is contagious until the last smallpox scab falls off.

Q: What is the smallpox vaccine?

A: The most common vaccine used today is made from the vaccinia virus, a close relative of the smallpox virus. Like all vaccines, it works by stimulating the body's disease-fighting immune system (see diagram, p. 10).

"Vaccinia and smallpox are so much alike that our immune systems have trouble telling them apart," Preston notes. As a result, he says, "within days, a vaccinated person's resistance to smallpox begins to rise."