Smallpox Strike Called Unlikely

It’s the ultimate fear in the post-9/11 era: Terrorists infect themselves with smallpox, then before the telltale pustules spread across their bodies, they spend a day at LAX -- talking, coughing, touching chairs and counters, spreading contagion via travelers to every corner of the nation.

Other scenarios are just as terrifying: the unleashing of a smallpox bomb that sprays a city with the deadly virus, or the release of genetically engineered smallpox for which there is no protection.

President Bush’s expected announcement today of a nationwide smallpox vaccination plan has pushed these visions of horror to the forefront of the public consciousness.

But as the government prepares for a possible smallpox attack, some experts say that such scenarios, while possible, are not likely.

Smallpox is difficult to handle and experts believe its victims are contagious for no more than a day before the excruciating rash erupts -- an obvious sign of infection that would immediately mark any carrier, said Clarence J. Peters, director of the Center of Biodefense at the University of Texas medical school in Galveston. Before the disease’s infectious phase, a would-be bioterrorist would show debilitating flu-like symptoms, making it difficult to move around in public inconspicuously. Peters said the disease also must be spread by close contact -- more than merely crossing paths with a carrier or brushing past the same ticket counter.

The scientific and technological challenges of creating smallpox bombs or genetically altered smallpox agents also make those possibilities somewhat distant, said Jonathan Tucker, author of “Scourge: The Once and Future Threat of Smallpox.” Advanced bioweapons would cost millions to develop, yet would be difficult to test for all but the most advanced nations because of the extreme danger.

“It’s still quite unlikely that smallpox would be used as a weapon,” Tucker said.

Smallpox was declared eradicated from the world in 1980. The only legal stocks of the virus that were not destroyed are small amounts held by the U.S. and Russia in highly secured labs. Today’s fears stem from former Soviet scientists who manufactured and maintained tons of the virus in violation of international law. Some of those experts may have sold deadly samples.

But even if terrorists obtain stocks of smallpox, suicidal efforts to provoke an epidemic would be easily prone to failure.

Life of Virus

Once a person is infected, the incubation period is seven to 17 days, followed by body aches, high fever and dizziness -- and often severe abdominal pain and even delirium. Yet the person would not be contagious until the appearance of a rapidly spreading rash, according to a consensus of the nation’s leading smallpox experts published in the Journal of the American Medical Assn. in 1999.

“The guy is going to feel terrible; he is going to be walking around, not shedding virus until maybe the day before, or the day of the rash,” Peters said. “He may be obviously ill, a fever, a flushed face and bumps on his face.”

If the carrier survives, contagion lasts until the very noticeable scabs from smallpox pustules have completely healed, three weeks or more later.

In a few cases, terrible outbreaks have been started by a single unwitting victim. For example, a Yugoslav Muslim contracted smallpox during a pilgrimage to Mecca in 1972, returned home and started an epidemic that eventually caused 150 cases, including dozens of deaths. In response, authorities imposed a massive quarantine and vaccinated millions.

Yet such single-source episodes are the exception, because smallpox is more difficult to transmit than many other infectious diseases. New contacts must have direct contact with viral particles shed from pustules on the skin, or those coughed up from the mouth or throat. Once in the open environment, the virus wouldn’t survive for long, experts say, except in cool, dry conditions.

This combination of factors has historically caused smallpox to spread more slowly than such childhood ailments as chickenpox. In general, smallpox victims pass the disease to family members or hospital workers, rather than casual contacts. Even the Yugoslav carrier spread contagion almost exclusively to hospital workers.

Unlike the Yugoslav authorities who were caught by surprise with their nation’s first smallpox episode in more than four decades, this country is on a high state of alert. The U.S. public health infrastructure is better equipped to rapidly respond to an outbreak, the vast majority of victims can be saved by taking the vaccine within three days of exposure and even as long as seven days after exposure, the vaccine can reduce the severity of the disease.

A lone, infected terrorist, or a small group “could certainly do some damage,” Peters said. “But he’s not going to cruise through [John F.] Kennedy [International] Airport and leave hundreds of people infected behind him. This whole scenario that there’s going to be massive spread by people that nobody notices is not realistic.”

Russian Weapons

In contrast, a smallpox bomb or sprayer that floats the virus over a wide area would be much more likely to spark an epidemic, experts say. Such weapons were developed in Russia well into the 1990s.

“Unfortunately, I know of a number of examples about possible involvement of some Soviet and Russian scientists in collaboration with some countries like Iraq and Iran,” said Ken Alibek, formerly a top scientist in the Soviet biological warfare program. He defected to the United States in 1992, and now directs a biodefense institute at George Mason University, in Manassas, Va.

Yet even with expert help, such weapons would be technically difficult to construct, said Peters, who formerly headed the Disease Assessment Division at the Army’s primary biological defense lab at Ft. Detrick, Md.

The smallpox virus must be grown in living cells, typically within fertilized eggs, he said, then refined under precise conditions. A gooey mass of smallpox-laden egg protein must be turned into a liquid or ultra-fine powder. It then must be packaged in a bomb or other disseminator that can gently release the microscopic particles so they are not destroyed and float freely in the air, Peters said.

Even if terrorist groups could overcome the technical problems, there is still a powerful disincentive for them to pursue such a strategy since developing the weapons would pose an enormous risk of accidental release.

Such stumbling blocks helped fuel a debate about how widely to vaccinate the population beyond health-care workers, soldiers and public safety officials. President Bush ultimately decided to offer the vaccine to all Americans on a voluntary basis when sufficient licensed supplies are available.

“It comes down to a weighing of risks,” Tucker said.

A terrorism-related smallpox epidemic could be contained with relatively few deaths, he said, but may still provoke widespread panic. In a national vaccination campaign many thousands of people would certainly suffer serious side effects, and as many as several hundred could die. Yet society as a whole might accept that toll as a fair price for a sense of greater security.

The most horrifying smallpox scenario -- the development of an altered strain engineered to defeat the vaccine -- gained currency last year. A team of Australian researchers spliced the gene for the human hormone interleukin-4, which affects immune response, into mousepox, a virus related to smallpox that cannot infect people. Their goal was innocent: They wanted to reduce mouse fertility.

Their result sent chills through the biodefense community. The experiment created a super mousepox strain that even killed mice that had been previously immunized.

Most exerts accept the possibility that a genetically engineered, super smallpox virus can be created. But aside from the tremendous dangers of handling so deadly and incurable a microbe, other drawbacks make them doubt anyone would try.

“You can add genes to smallpox, but what we don’t know is whether you are getting the effect you want,” Peters said. “I could never be sure it was a decent [biological warfare] agent unless I tested it.”

Testing on humans would be a monumental gamble. Because only people contract smallpox, the weapon’s effectiveness could not be tested on animals.

Such concerns reflect a more general skepticism about the efficacy of medical defenses against bioterrorism. Many diseases beyond smallpox have been turned into weapons in the past, so a sophisticated attacker might avoid smallpox if the target population has been vaccinated, and instead use a weapon such as plague or anthrax. Vaccinating against every possible threat is next to impossible.

“When you talk about biological terrorism, I would not spend even a penny on vaccines,” Alibek said. “Protecting an entire population [in advance] against biological warfare is not feasible.”

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(BEGIN TEXT OF INFOBOX)

The disease

Caused by the variola virus, smallpox is an ancient and highly contagious disease. The most serious form has a fatality rate of 30% or more. In the 20th century alone, an estimated 300 million people died of smallpox worldwide. Here’s a look at the disease and its history:

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Exposure

How it spreads: Spread by inhaling infected saliva droplets, usually through coughing; direct contact with scabs, bedding or contaminated clothing.

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Phases and duration

Incubation period (seven to 17 days) -- Not contagious

Initial symptoms (two to four days) -- Sometimes contagious.

First symptoms include fever, malaise, head and body aches.

Early rash (About four days) -- Most contagious

Pustular rash (About five days) -- Contagious. Rash turns into small blisters that become pustules.

Pustules and scabs (About five days) -- Contagious

Resolving scabs (About six days) -- Contagious

Scabs resolved -- Not contagious

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Treatment/Prevention

Vaccination: Will prevent infection up to 10 years. The vaccine contains another live virus called vaccinia. It does not contain smallpox virus. The vaccine can produce serious side effects, from severe rashes to brain inflammation, killing an estimated

one in 1 million.

Treatment: There is currently no proven treatment or cure, but vaccine given within four days of exposure can lessen severity.

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Vaccine stockpiles

There are currently enough doses to vaccinate everyone in the U.S. in case of an outbreak. Fully licensed vaccine will become available by 2004.

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Sources: Centers for Disease Control and Prevention; American Medical Assn.; Johns Hopkins University; and Times archives.

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Researched by Maloy Moore/Los Angeles Times