As a result of the WHO programme of case detection and vaccination, it is confidently believed that smallpox has been eradicated world-wide. Apart from two laboratory-acquired infections in 1978, the last known case occurred in Somalia in 1977.

Major smallpox produced a severe constitutional illness associated with a peripherally distributed rash with lesions which, in any one area, progressed in unison from macules through papules, and vesicles, to pustules. The mortality rate was as high as 40%.

A similar virus causes monkeypox in primates in jungle areas of Central Africa, with lesions resembling those of smallpox. Some human cases have occurred in those in contact with infected primates but interhuman spread is seen exceptional .

The virus of smallpox is maintained in two designated laboratories, one in the USA and the other in Russia, in order to be able to differentiate such diseases as monkey pox from smallpox. Only staff employed in these designated laboratories now require to be vaccinated against smallpox. Limited stocks of smallpox vaccine are available for this purpose, and in case the disease should reappear.

Vaccinia virus is derived from cowpox virus (originally shown by Jenner to prevent smallpox) and is a distinct poxvirus. It is used as the live vaccine for smallpox, as it elicits cross-protective immunity to smallpox virus. Complications of vaccination include progressive vaccinia in immunodeficient subjects due to dissemination from the vaccine site, eczema vaccinatum in patients with eczema, and fetal vaccinia in pregnant women given vaccine. Generalised vaccinia refers to self-limiting blood-borne spread of vaccinia in normal recipients. Post-vaccinial encephalitis was very rare.


This common and easily recognised poxvirus infection usually affects children and atopic or immunocompromised adults. Spread is by direct contact or by infected towelling, clothing etc. The incubation period is 2-6 weeks.

Clinical features

Individual lesions are shiny, white and hemispherical and grow slowly up to about 0.5 cm in diameter. Their characteristic umbilicated look is due to a central punctum which may contain a cheesy core. Multiple lesions are common . Like warts, many lesions will clear spontaneously, often after brief local inflammation.


No treatment may be best in some children but cryotherapy or rapid expression is tolerated well by others, especially if performed by an experienced operator.

Concepts of infection
Major manifestations of infection
Principles of management of infection
Diseases due to viruses
DNA viruses
Diseases due to chlamydiae
Diseases due to rickettsiae
Diseases due to bacteria
  • Streptococcal infections
  • Staphylococcal infections
  • Corynebacterial infections
  • Bacillus infections
  • Bordetella infections
  • Salmonella infections
  • Food poisoning
  • Dysentery
  • Other true bacterial infections
  • Mycobacterial infections
Diseases due to spirochaetes
  • Leptospira infections
  • Borrelia infections
  • Treponema infections
Diseases due to fungi (mycoses)
  • Cutaneous fungal infections
  • Subcutaneous fungal infections
  • Systemic fungal infections
Diseases due to protozoa
Diseases due to helminths
  • Trematode (fluke) infections
  • Cestode (tapeworm) infections
  • Nematode (roundworm) infections
  • Zoonotic helminth infections
Diseases due to arthropods
Sexually transmitted diseases
  • Sexually transmitted bacterial diseases
  • Sexually transmitted viral diseases
  • Miscellaneous conditions