By Lisa Ellis
InteliHealth News Service

It was the scourge of nations for thousands of years, killing kings and peasants alike, devastating the empires of the Aztecs and Incas and other nations of the New World, and still producing at least 10 million annual cases as late as the 1960s.

Yet smallpox, the disfiguring disease caused by the variola virus, also was the object of one of the most successful public-health campaigns in history. Widespread vaccination, detection and isolation of people with the illness, and containment measures steadily loosened the grip of smallpox until the World Health Organization declared in 1980 that it had been wiped out.

No one has contracted smallpox since 1978.

Only two nations, the United States and Russia, are known to have stocks of the virus, which are kept in secured laboratories.

Yet the U.S. government recently announced the first major U.S. smallpox vaccination campaign since 1972, when routine inoculation was halted. Officials say the campaign is a precaution in case some rogue nation or group has obtained a supply of the virus for use as a weapon.

Plans call for vaccination of up to 10 million volunteer medical workers, emergency "first responders" and certain military personnel. The government is discouraging vaccination of the public because the vaccine can cause serious complications and about one death for every million people who receive it.

Meanwhile, the public needs to know more about the disease, particularly how it is — and is not — transmitted, to prevent unnecessary fears, says Joel G. Breman, a physician specializing in infectious diseases and tropical public health who participated in the 1966-1980 campaign to eliminate the disease.

How Smallpox Is Transmitted

Although the disease is contagious — it is spread from person to person — it is not as contagious as the flu, measles or chickenpox. You don't always contract it if exposed to someone who has smallpox, says Dr. Breman, a senior scientific adviser at the Fogarty International Center, part of the U.S. government's National Institutes of Health.

"It is spread only by close personal contact, face to face with a patient who has already manifested the disease, with a rash," he says.

In other words, in most cases you have to be pretty close — within perhaps six feet — of a person who's already showing smallpox's most obvious symptom, a distinctive rash that typically starts on the face, arms and legs. Although the disease at times has been mistaken for chickenpox or other rashes, symptoms of smallpox are not subtle.

"People think that someone who's incubating the disease [and has no rash] can transmit it, but that's not the case," he says. "That's why most of the transmission comes in the home or in the hospital."

Smallpox is primarily spread through coughing and in the tiny droplets expelled when you breathe, as well as in saliva, Dr. Breman says.

Infected bedding and clothing also can spread the virus. Smallpox also has been spread through a building ventilation system, but such cases were "exceedingly rare," Dr. Breman says. Cases spread by contact on public transportation also were rare.

Also minimizing transmission is the fact that the disease at its most infectious stage is not only debilitating but scary-looking, says Thomas M. Mack, M.D., M.P.H., a professor of preventive medicine at the University of Southern California.

"People who are infectious are very, very sick and they look very, very sick, so nobody would get near them," says Dr. Mack, who studied the spread of smallpox in Asia in the 1970s. "It's most contagious in the last half of the first week of rash."

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Death And Disfigurement

Smallpox altered world history because of the deaths of monarchs. It contributed to the destruction of most of the native population of the Americas after conquerors brought the disease from Europe. By the end of the 18th century, when Edward Jenner developed the first smallpox vaccine, the disease killed 400,000 people a year in Europe, according to a World Health Organization report.

All of this occurred because smallpox and its complications can be so deadly. There are several types of smallpox, and their severity varies. But the most common type, variola major, historically has killed 25 percent to 30 percent of people who get infected.

But death rates have varied considerably depending on age and vaccination status. "Very young children, under 5 and particularly under 1, would have mortality rates of above 50 percent in some outbreaks," Dr. Breman says. These rates also often applied to older adults — in the past, over age 50. Older children and younger adults, on average, had somewhat lower death rates.

There is still no specific treatment for smallpox, but medical practice has made many advances since these mortality rates were recorded. It is impossible to predict what the mortality would be if an outbreak occurred now, but it could be lower than historic rates.

Vaccination also made a difference, even if a person was vaccinated after exposure or too long ago to have full immunity. People vaccinated 10 to 20 years before an outbreak might still get sick, but often less severely and with lower death rates, says Dr. Breman, who recently published an article on the Boston outbreak of 1901-03.

In addition, vaccination within four days of exposure to someone with smallpox may completely prevent infection, he says. Even if you vaccinate someone a little later, but before symptoms appear, death rates are reduced, he says.

Of those who survived smallpox, a majority were left with disfiguring scars. Many developed eye infections that led to blindness.

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Recognizing Smallpox

Like many other conditions, smallpox causes a rash that develops into raised bumps. In the past, it has been confused with chickenpox, a drug allergic reaction, severe acne, insect bites, syphilis and several other conditions.

But these characteristics set smallpox apart, according to the World Health Organization:

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Controlling An Outbreak

U.S. government policy on handling any smallpox outbreak is expected to use the following strategy, according to documents from the U.S. Centers for Disease Control and Prevention (CDC):

These steps, along with strict infection-control measures at hospitals and laboratories connected to the outbreak, would help to break the cycle of transmission.

"The first and most important single thing is trying to get the doctors and even the public to recognize a case early so the person can be isolated and treated immediately," Dr. Mack says. Quick isolation of cases can minimize the spread of the disease, he says.

There is no known specific treatment for smallpox, although several possible agents are under investigation. Patients would receive appropriate fluids, nutrition, and treatment of their symptoms and any additional infections that developed.

No one knows how many cases of smallpox would result from an introduction today, when most people have little or no immunity. People under 30 have not been vaccinated. Experts say it's not clear what degree of immunity, if any, may remain in people vaccinated before 1972.

Physicians also are no longer familiar with smallpox. But the CDC, the World Health Organization and various physicians' organizations have widely disseminated information on smallpox in the last year to help educate doctors and the general public, Dr. Breman says.

In addition, he says, the U.S. local, state and national epidemic-response system is more prepared than ever to contain any outbreak.

"We have much better developed detection and response systems for any epidemic in our country," he says. "Globally, it's still pretty difficult to respond because of the overwhelmed and inadequate health-delivery systems in low-income countries. Here we have people who are trained, who are vigilant, who know what to do if they see a suspect patient. They do this for many diseases every day."

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