Smallpox is an acute contagious disease caused by variola virus, a member of the orthopoxvirus family. Smallpox, which is believed to have originated over 3,000 years ago in India or Egypt, is one of the most devastating diseases known to humanity. For centuries, repeated epidemics swept across continents, decimating populations and changing the course of history. Smallpox was eradicated by a collaborative global vaccination program led by the World Health Organization. The last known natural case was in Somalia in 1977.


Symptoms of smallpox

Incubation period of smallpox is usually 12–14 days during which there is no evidence of viral shedding.

The incubation period is followed by the sudden onset of influenza-like symptoms including fever, malaise, headache, prostration, severe back pain and, less often, abdominal pain and vomiting. Two to three days later, the temperature falls and the patient feels somewhat better, at which time the characteristic rash appears, first on the face, hands and forearms and then after a few days progressing to the trunk. The resulting spots become filled with clear fluid and later, pus, and then form a crust, which eventually dries up and falls off. All lesions in a given area progress together through these stages.

The sequellae are scars and blindness.

Smallpox was fatal in up to 30% of cases.


Epidemiology and vaccination against smallpox

Smallpox affects only humans. The disease is transmitted after fever has begun and during the first week of rash, through respiratory contact or contaminated clothes or bedding.

There is a vaccine to protect from smallpox and it was a key tool in the eradication of the disease. The vaccine does not contain the Variola virus which causes smallpox, but a closely related virus called vaccinia.

Smallpox no longer occurs naturally since it was totally eradicated by a lengthy and painstaking process, which identified all cases and their contacts and ensured that they were all vaccinated.

The smallpox vaccine led to the global eradication of the disease, certified by a commission of eminent scientists in December 1979 and subsequently endorsed by the World Health Assembly in 1980. Until then, smallpox killed millions of people.


Vaccines against smallpox

After September 11 2001, as a producer of the vaccine, sanofi pasteur has taken the initiative of making the stores of smallpox vaccine that remain available to health authorities in different countries, including France and the United States.

To be able to anticipate a potential bioterrorism attack, sanofi pasteur has also developed a second generation smallpox vaccine. In 2008, sanofi pasteur acquired Acambis, a company that also produces a smallpox vaccine.



World Health Organization. The smallpox pages (path: Programs and projects / Epidemic and Pandemic Alert and Response (EPR) / Diseases covered by EPR / Smallpox), available at Accessed November 2008 17.