A CONSIDERABLE RISK: Among the infectious agents that might be used as terrorist weapons, the smallpox virus represents a sufficiently high risk, which is difficult to manage and must be seriously taken into account.
From a microbiological point of view: Two viral strains of the smallpox virus, which belong to the Poxviridae and orthopoxvirus-type families, are known. They are associated with various clinical presentations of smallpox, i.e., variola major and variola minor or "alastrim".
Variola major: Five clinical forms of varying prognosis are described. Common smallpox, haemorrhagic smallpox (the most severe form of the disease), mild smallpox (predominantly observed in vaccinated patients), flat-type smallpox (defined by coalescent and slowly progressive lesions) and so-called "sine eruptione" smallpox.
Variola minor: This form is not as severe as variola major and the mortality rate is lesser.
Diagnosis: Smallpox must be systematically evoked on clinical elements and confirmed by electronic microscopy of a sample of liquid from a vesicle or pustule or a scab. The strains can be characterised by PCR (Polymerase Chain Reaction).
Treatment: It is symptomatic. Early vaccination, within 4 days following exposure to the virus, permits the reduction in mortality by 50%. The only efficient prevention is vaccination prior to any exposure to the virus. In the case of a bioterrorist attack, the United States and most of the EC countries propose to vaccinate only the health professionnals most exposed to the virus and those having contacted identified cases.