Oct. 24, 2001 -- Say "worst-case scenario" to any bioterror expert and you'll get a one-word reply: smallpox.
Since Sept. 11, 2001, the world has learned to imagine the unimaginable. It's hard to think of why anyone would bring back "the most terrible of the ministers of death," as 19th century historian Thomas Babbington Macaulay called it. The eradication of smallpox, announced in 1980, ranks among the greatest of human achievements.
Few diseases are as contagious, as deadly, or as horrible as smallpox. It killed at least 300 million people in the first 80 years of the 20th century -- more than three times the number killed in all the world's wars. Because few people now have any natural or vaccine immunity, new bouts of the disease would be far more deadly.
Donald A. Henderson, MD, MPH, oversaw the international smallpox eradication effort. He's now director of the Johns Hopkins Center for Civilian Biodefense Studies and serves as bioterror advisor to the federal government. Henderson spoke with WebMD in January 2001.
"The probability of an attack by terrorists using the smallpox virus, we feel to be very low, for a number of reasons," Henderson says. "To obtain and grow organisms like smallpox ... is [very] complicated and is not so easily done by persons with only limited training. However, the Soviet Union produced large amounts of organisms of various types, and the laboratories which produced those are now very poorly funded. Many of the scientists have left the laboratories, and some have been recruited to work in other countries. Thus, there is the possibility that individuals with bioterrorism in mind could recruit Russian expertise at very little cost or might be able to obtain some of the finished material ready for use."
As small as this risk may be, Henderson says a release of smallpox today would be "a major catastrophe." This is also the opinion of C.J. Peters, MD, former chief of special pathogens at the CDC and now professor of microbiology at the University of Texas Medical Branch, Galveston.
"We are worried that other people might have smallpox and would use it to start a smallpox epidemic. That is why the governmenthas 7 1/2 million doses of smallpox vaccine stored away and why they are contracting to take 300 million more doses," Peters tells WebMD."The government has had much experience with smallpox in the past.Cases were introduced in the 1960s and 1970s from overseas.And it was possible to stop smallpox transmission by vaccinating all the people in contact with the cases."
Plans are underway to stretch existing smallpox vaccine doses to cover three or even five times as many people. This stopgap measure is of critical importance. The only way to stop a smallpox outbreak is to vaccinate a ring of people who have been around infected people.
People with smallpox are contagious only after they begin to get the awful rash that gives the disease its name. This means that once an outbreak is known to be under way, people with the rash are unlikely to infect anybody except for caregivers. These are the people who first should get the vaccine.
During very small outbreaks, patients can be kept in isolated hospital rooms. In larger outbreaks, patients would have to be kept at home. In either case, limited vaccine supplies would be rationed to the people surrounding each case. This strategy worked in previous outbreaks prior to smallpox eradication. Even then -- when most of the population had been vaccinated as children -- there was terrific pressure for mass vaccinations. Controlling mass panic is the most troublesome aspect of dealing with a smallpox attack. If sufficient vaccine is not on hand, some experts fear that the government will have no option other than forcible quarantine of exposed people.
Once the U.S. government has its 300 million doses of smallpox vaccine, the question is what to do with it. Some experts favor routine vaccination for everyone preemptively; others would reserve the vaccine to use only in the event of an outbreak.
The smallpox vaccination isn't completely safe. In the U.S. in 1968, for example, some 14 million people received the vaccine. That year there were 572 bad reactions resulting in nine deaths -- more people than have died so far in the current anthrax bioterror attack. In those days, bad reactions were treated with serum (a component of blood) from people who recovered from infection with smallpox -- and now this serum is in very short supply.
Unknown is what effect vaccination might have on people whose immune system isn't working right -- such as those with HIV infection or those taking immune-suppressing drugs for arthritis. Pregnant women also are at increased risk of bad reactions to vaccination. However, these populations also would be at increased risk of fatal smallpox -- so the risk of vaccination would have to be weighed against the risk of infection.
Other smallpox facts:
- Routine smallpox vaccination ended in 1972. The military stopped vaccinating its personnel in 1990.
- Vaccine protection lasts for about 10 years in those who receive a single dose -- so most people vaccinated as children are no longer immune. People vaccinated twice appear to be protected for 30 years. Laboratory workers who handle smallpox get vaccinated every 10 years.
- People who received at least one smallpox vaccination probably would get less serious disease if infected. In the case of a major smallpox attack, with too little vaccine to go around, these people might be called upon to care for the sick.
- Destruction of remaining smallpox stores in the U.S. and Russia was postponed to determine whether there is any scientific use for the virus. Some researchers think the virus might teach us a few things. Others (Henderson chief among them) say that the risk of keeping the virus far outweighs any possible benefit.
- If released into the environment, smallpox would be undetectable. It can survive in the air only for 24 hours under the best of conditions. Because it usually takes an infected person 12 to 14 days to develop symptoms, it would be very hard to trace an aerosol release.
- The bed sheets and clothing of people with smallpox can be infectious for extended periods after contamination. Such laundry must be handled with care and washed in hot water to which bleach has been added.
- Smallpox scabs contain infectious virus for as long as 13 years, but they do not release the virus into the environment. This is because the virus gets trapped in the scab.