Smallpox

Smallpox was a serious illness that killed hundreds of millions before its eradication. It caused a hard, blistering rash that often led to disfiguring scars. About 1 in 3 people who got smallpox died from it.

Beginning in the 1960s, the World Health Organization (WHO) led efforts to stop the spread of smallpox worldwide. By vaccinating and controlling outbreaks, they rid the world of smallpox. It was eradicated in 1980. The last naturally occurring case was in 1977.

Does smallpox still exist?

Smallpox no longer exists in humans or spreads naturally. There haven’t been any cases of smallpox in the last 45 years. Two laboratories (one in the U.S. and one in Russia) have stocks of the virus that causes smallpox for research purposes only.

How did we eradicate smallpox?

Some factors that may have contributed to successfully eradicating smallpox include:

• Only humans get smallpox. It doesn’t spread through animals or insects. This means fewer ways to get infected.
• It was easy to identify. Everyone who had smallpox had symptoms, including a characteristic rash. No one carried smallpox without knowing it (no asymptomatic carriers).
• It spread relatively slowly. Smallpox usually wasn’t contagious until an infected person was too sick to be around many other people. It typically spread among people living in the same house.
• Ring vaccination contained outbreaks. Because it spread only among close contacts, health officials could contain smallpox outbreaks with “ring vaccinations.” This meant vaccinating just those who had been around an infected person recently (a “ring” of contacts).
• It had been around for thousands of years.Survivors of smallpox already had immunity. This meant that fewer people needed to be vaccinated to stop the spread.