Small pox which was once a killer disease wreaking havoc around the world was declared eradicated by the WHO on 8th May 1980. The following factors helped in eradicating small pox.
- Small pox has no known animal reservoir
- There is no long term carrier state
- Infection produces lifelong immunity
- Subclinical infections are not communicable
- The disease was easily identified by its characteristic rash
- The vaccine was effective and heat stable
- There was international cooperation in eradicating small pox