FREE subscriptions for doctors and students... click here
You have 3 more open access pages.

Smallpox (variola) is a DNA virus of the genus orthopox virus, which includes vaccinia and monkeypox.

  • it is specifically a human disease with no reservoir in any animal species
  • in normal environmental conditions (ambient temperature, ordinary levels of humidity and exposure to sunlight) the virus is very unlikely to survive for more than 48 hours (1)

The infection no longer exists in nature, having been declared eradicated in 1980 following a global campaign led by the WHO.

  • the virus has been retained legally under strict security in two World Health Organisation (WHO) collaborating centres: the Centers for Disease Control and Prevention (CDC), Atlanta, USA and the Laboratory for Applied Microbiology at Koltsovo in Novosibirsk Region, Russian Federation

Although it is highly unlikely, a concern about re-emergence of the disease due to deliberate release of the organism as a biological weapon remains. Without containment measures, this would almost certainly lead to rapid spread because;

  • the majority of the population of the United Kingdom, as elsewhere, is susceptible, vaccination having ceased in the 1970s
  • population mobility is far greater than thirty years ago
  • there may be delays in diagnosing the disease due to clinicians’ unfamiliarity with the presenting features (1)


Last reviewed 01/2018