Smallpox: Health Significance And Clinical Manifestations
The Small Pox Pandemic
A General Overview Of Small Pox
Small pox is a natural infection in man caused by variola virus and the virus is seen only in man. The virus is 200 to 250 nm in size and belongs to the group of pox viruses which are DNA viruses. The virus is transmitted from man to man by respiratory route. There are no animal reservoirs or insect vectors in the transmission of this diseases. The transmission may be direct from patient to patient or through formites and other contaminated articles. Nasopharygneal secretions, vesicle fluid and dried scabs contain the virus. The virus can remain viable in dried scab for over one year. A patient is infective from the onset of early symptoms till the last scab has fallen off.
Though smallpox was one of the most dreaded diseases and outbreaks occurred in the tropics regularly, at present, the disease has been eradicated by worldwide efforts undertaken by the WHO from 1967 to 1977. The world was declared free of natural infection in October 1977. Except for the stock cultures of the virus maintained in a few laboratory, the virus is believed to have disappeared. This achievement was made possible by an intensive program of mass vaccination and early case reporting. Absence of any non-human reservoir and vector and the solid immunity produced by vaccination have made this achievement a reality. After entry, the virus reaches the lymph nodes, where it multiples and then enters the circulation. The skin and mucous membranes are effected thereafter. The effected epithelial cells show acidophilic cytoplasmic inclusion bodies called Guarnieri bodies. These are aggregates of the viral particles which are called Paschen bodies.
Small Pox Manifestation On The Skin
Clinical Presentations of Small Pox
The incubation period is 12 days (8 to 16 days). Prodromal symptoms occur 2 to 4 days before the eruptions start. These consist of high fever, myalgia, headache, backache, delirium and abdominal pain. The rash starts on the third day and the fever subsides when the rash appear. Fever reappears after varying intervals when the rash becomes pustular. The temperature comes down with scabbing. The rashes are characteristic. They are distributed on a centrifugal pattern. The face, arms and legs are more often and more heavily affected. Presence of vesicles in the palms and soles is characteristic. Initial lesions are erythematous macules, which progress successively into papules, vesicles and pustules and scabs at 48 hour intervals. The vesicles and pustules are deep set in the skin, multiloculated and the center is umbilicated. Unlike as in chicken pox, all the vesicles are at the same stage of development. When the scab separates, pitted scars are left behind, which tend to remain permanent.
In vaccinated individuals, who possess residual immunity, the clinical picture is modified and this is termed varioloid. This is abrupt in onset with the development of only a few rashes. The course is benign. Small pox may occur without the characteristic rash “Variola sine eruption”. A less virulent form of the virus capable of producing milder manifestations, ‘variolar minor” (alastrim), has also been recognized.
Other serious clinical types may occur less commonly. These are hemorrhagic smallpox which is highly fatal and the flat form in which the papules are velvety, which may become vesicular and lead to peeling off of the whole epidermis.
© 2014 Funom Theophilus Makama