There are two types of severe smallpox that are usually fatal.
Two types of severe smallpox include:
- Hemorrhagic smallpox
- Malignant smallpox
Hemorrhagic smallpox starts suddenly, with a high fever, headache, back pain, and abdominal pain. This is followed by a red rash, which causes bruising and broken blood vessels to form under the skin. Death occurs within a week of the onset of the rash.
Malignant smallpox, like hemorrhagic smallpox, presents with rapid onset of symptoms. However, the rash starts slowly, and skin lesions do not turn into pustules. The rash has a soft, flat, velvety character, which may cause large areas of the skin to peel. Usually, death occurs within one week of the onset of symptoms.
- Heymann DL. Smallpox containment updated: considerations for the 21st century. Int J Infect Dis. 2004 Oct;8 Suppl 2:S15-20. 
- Kerrod E, Geddes AM, Regan M, Leach S. Surveillance and control measures during smallpox outbreaks. Emerg Infect Dis. 2005 Feb;11(2):291-7. 
- Woods R, McCarthy T, Barry MA, Mahon B. Diagnosing smallpox: would you know it if you saw it? Biosecur Bioterror. 2004;2(3):157-63.