SMALLPOX

also called variola, one of the world's most dreaded plagues until 1977, when it was declared eradicated. The disease was described as early as 1122 BC in China and is referred to in ancient Sanskrit texts of India. The mummified head of the Egyptian pharaoh Ramses V (died c. 1156 BC) bears evidence of the disease. Smallpox is an acute infectious disease caused by a virus, characterized by fever and, beginning about two days later, an eruption that, after passing through the stages of papule, vesicle, and pustule, dries up, leaving more or less distinct scars. The characteristic eruption may be so profuse as to be confluent, especially on the face, or so scanty that the lesions are missed altogether. Modifications, both toward fewer lesions and toward their being more superficial, may occur either naturally or because of vaccination that was not recent enough to give complete protection against the disease. With nearly complete vaccinal protection, few lesions will appear; but even if vaccination has been effected many years before, smaller and more superficial lesions are the rule in cases in which an unvaccinated person would have a severe attack. Such superficial lesions are also characteristic of the naturally occurring mild strains of the disease (variola minor). Besides the characteristic focal eruptions (papule to vesicle to pustule to scab to scar), there is sometimes a toxic eruption during the initial fever, before the appearance of the true smallpox rash. These toxic rashes may be diffuse blushes on trunk or limbs, somewhat suggestive of scarlet fever or measles; they may, on the other hand, be deeper red, with small hemorrhages like fleabites or larger blotches in the skin. The first type of rash is clinically unimportant, but the deep red, hemorrhagic rash occurs in the most severe, usually fatal cases of the disease. Frequently such patients die before the true smallpox rash has time to develop, and the disease is not diagnosed. These cases are not usually sources of infection, however, because smallpox is not infectious until the characteristic focal eruption comes out in the throat and on the skin. Each case of smallpox arises from contact, direct or indirect, with another case of the disease. There are no natural animal carriers or natural propagation of the virus outside the human body. The virus is very stable and can survive for long periods outside the body. It has survived in bales of cotton for 18 months; because of this longevity clothing or bed linens contaminated by a smallpox patient can be a source of infection, and in outbreaks in Europe this means has often been shown to have spread the disease. The virus can also survive dried in dust, probably for several months, making disinfection of wards or sickrooms after the removal or death of a patient essential. Most victims are, however, infected by contact with an infected person by inhalation of the virus expelled in the breath or mouth spray. Despite the hardiness of the virus, smallpox is not a highly infectious disease; a patient does not usually infect more than one or two of his closest contacts. The great danger from the disease is that it can cause very mild attacks in vaccinated persons, and these persons can spread the fatal form of the disease to their contacts without knowing that they themselves have been infected. It is therefore essential in dealing with an outbreak to make thorough enquiry into all possible contacts of patients and to follow these contacts until it is certain they have escaped infection or to isolate them at once if they show any sign of infection. The smallpox virus exists in one main strain, variola major, and a vaccine prepared from variola major will also protect against the one or two other closely related strains, such as variola minor, which causes a much milder form of the disease. The availability of one single-type vaccine against all forms of clinical smallpox, combined with the absence of any reservoir of smallpox virus in nature, made possible the attempt by the World Health Organization to eradicate smallpox from the world. This immense project involved following all contacts of every case of smallpox and vaccinating them in time to prevent the spread of infection. The project is believed to have been successful. Smallpox is estimated to have caused 2,000,000 deaths in 1967. No cases were reported from 1977 to 1980, with the exception of two cases in England in 1978 whose source was virus in a laboratory. Routine smallpox vaccination has been discontinued in most countries, and the virus is to be kept in not more than four laboratories throughout the world, ready to make vaccine should it ever again be necessary.