Smallpox was once found throughout the world, causing illness and death wherever it occurred. Smallpox was primarily a disease of children and young adults, with family members often infecting each other.
A massive program by the World Health Organization (WHO) eradicated all known smallpox viruses from the world in 1977, except for samples that were saved by various governments for research purposes. The vaccine was discontinued in the United States in 1972. In 1980, WHO recommended that all countries stop vaccinating for smallpox.
In 1980, WHO also recommended that the remaining virus samples be transferred to two WHO laboratories for storage. Those laboratories were the Centers for Disease Control (CDC) in Atlanta, Georgia, and a laboratory in Russia. Russia, however, started a program to produce the smallpox virus in mass quantities, specifically for bombs and other weaponry.
Some believe that other countries such as Iraq, Iran, and North Korea may also hold some stores of the smallpox virus. Researchers continue to debate whether or not to kill the last remaining samples of the virus, or to preserve it in case there may be some future reason to study it.
According to the CDC, since the vaccine has not been administered in the U.S. since 1972, those persons who had received the vaccine in the past are likely susceptible now (as are those who have never been vaccinated). It is not known how long previous vaccinations would remain effective, but it is unlikely that people would still have a high enough level of immunity to protect against the virus.
Risk factors for smallpox include being a laboratory worker who handles the virus (rare), or being in the environment where the virus was released as a biological weapon.
THE RISK OF TERRORISM
It is conceivable that smallpox could be deliberately reintroduced into the population. Smallpox could be released by aerosol, and it would spread easily because the virus remains very stable in aerosol form.
It would take no more than 50-100 cases to cause legitimate concern on an international level. Emergency measures would need to be taken immediately.
Smallpox is highly contagious from one person to another. It is most contagious during the first week, and is spread from saliva droplets. It may continue to be contagious until the scabs from the rash fall off. It may also be spread from bed sheets and clothing.
Researchers believe that the smallpox infection (if released in aerosol form, under favorable conditions, without sunlight) could remain viable for as long as 24 hours. In unfavorable conditions, the virus may only remain viable for 6 hours. There is clear evidence that shows that the virus can remain viable on bed linens and clothes for significant periods of time.
