chapter  13
6 Pages

Guides for Emergency Response: Biological Agent or Weapon: Smallpox (Variola)

Guides for Emergency Response: Biological Agent or Weapon: Smallpox (Variola) AGENT: Smallpox virus, an orthopoxvirus with a narrow host range confi ned to humans, was an important cause of morbidity and mortality in the developing world until recent times. Eradication of the natural disease was completed in 1977 and the last human cases from laboratory infections occurred in 1978. Appearances of human cases outside the laboratory would signal use of the virus as a biological weapon. Under normal conditions, the virus is transmitted by direct (face-to-face) contact with an infected case by formites (objects, such as clothing, towels, and utensils that possibly harbor a disease agent and are capable of transmitting it), and occasionally by aerosols. Smallpox virus is highly stable and retains infectivity for long periods of time outside the host. A related virus, monkeypox, clinically resembles smallpox and causes sporadic human disease in West and Central Africa. Smallpox is a highly contagious virus with fever and a blister-like rash. Smallpox can survive for centuries, and antibiological drugs are not able to handle viruses. It is caused by two species of pox-virus, variola major or variola minor; the disease is only carried by humans. Since vaccination with vaccinia throughout the world, not one case of natural smallpox has occurred. Only two samples of this virus are known to still exist in the world; one at the Center for Disease Control and Prevention in Atlanta, Georgia, and one at the Vector laboratory in Novizbersk in the former Russia. Smallpox has a death rate of about 30 percent for unvaccinated persons and three percent for those who have been vaccinated. Since smallpox has been exterminated in the world, civilians and military personnel have not been vaccinated for smallpox since the 1980s. You are unprotected if your vaccination is three or more years old. If you are old enough, you probably remember the smallpox vaccine scarifi cation method; paint the vaccine on your arm and then get jabbed sixteen times with a sharp needle. Pregnant woman, and carriers of HIV, or other immunity diseases should not be vaccinated for smallpox. As the skin becomes pock-marked and sloughs off , smallpox can easily be confused with chicken pox although lesions are a smooth, orderly progression in contrast to chicken pox.