Diagnosis of Smallpox

Strain Variations of Smallpox

There are two main strains of smallpox, variola major and variola minor. Variola major, the more severe of the two, has two different forms and numerous presentations which effect the severity and mortality rate.

Variola major

Variola major is the more common form, and was the only form known until the end of nineteenth century. (19:3) It has a more severe, more extensive rash, a higher fever, and a greater degree of prostration. (19:3) The fatality rate of variola major is 30% or higher. (19:3)

There are four clinical types of Variola major: ordinary, modified, flat and hemorrhagic. (19:5) The four clinical presentations of variola major, are based on the nature and evolution of the lesions. The relative vigor of the immune response probably determines the clinical presentation. (22:V3:23)

Ordinary Smallpox

Ordinary smallpox comes in two basic forms: the discrete type and the confluent type. (15:42) In the case of discrete ordinary smallpox, the pustules stand out on the skin as separate blisters, and the patient has a better chance of survival. In confluent-type ordinary smallpox the blisters merge into sheets, and it is typically fatal. [There is little normal skin appearing between the pustules.] Ordinary smallpox can also be Semi-confluent, where the pustules are extremely close together on the face, but are discrete elsewhere on the body. (22:V3:28) More than 90% of cases in both vaccinated and unvaccinated persons are of the ordinary type, which corresponds to the classical description of smallpox. (22:V3:7)

Modified Smallpox

Modified smallpox is a relatively milder in comparison to the other types of variola major, and primarily occurs in previously vaccinated people. (22:V3:25) Modified refers to the character of the eruption and the rapidity of its development. The prodromal illness still occurs but may be less severe than in the ordinary type. There is usually no fever during evolution of the rash. The skin lesions tend to evolve more quickly, are more superficial, and may not show the uniform characteristic of more typical smallpox. The lesions are often few in number, but could be numerous, or even confluent. Regardless of the number of lesions, they usually evolve rapidly. Modified smallpox is rarely, if ever, fatal, with death rates historically being 1% or less.

Flat Smallpox

Flat smallpox (or malignant smallpox) is characterized by an abrupt onset and prostrating constitutional symptoms that are similar to hemorrhagic smallpox (i.e. high fever and head, back and abdominal pain). (9:4) Like hemorrhagic smallpox, flat smallpox has a high mortality rate and often results in death. The confluent lesions develop slowly, never progressing to the pustular stage but remaining soft, flattened, and velvety to the touch. (9:4) The skin has the appearance of a fine grained, reddish-colored crepe rubber, sometimes with hemorrhages. (9:4) If the patient survives, the lesions gradually disappear without forming scabs or, in serious cases, large amounts of the epidermis might peel away. (9:4) The rash on the tongue and palate is usually extensive, and the skin lesions develop very slowly. (22:V3:31) It’s not known with certainty why some people develop this type of disease, but many cases occurred in children. (22:V3:31) The clinical course of flat smallpox is like that of burn or Stevens-Johnson Syndrome patients. (22:V3:32-38)

Clinical symptoms of flat type smallpox include: sudden onset, Temperature ranging between 38.3¾C & 38.9¾C, Malaise, headache, general muscle aches, backache (often severe), chest pain and anxiety… characterized by a “peculiar mental alertness”. Patients can also have abdominal pain, vomiting, and melena because of mucosal/submucosal hemorrhage. In cases involving mucosal/submucosal hemorrhage an acute abdomen may lead to laparotomy. Symptoms associated with days 2 & 3 include: tachycardia, irregular petechial and macular rash of chest, neck, back, upper arms, dusky erythema of face: marked intracuticular edema, and a scalded appearance of skin, like severe sunburn. Vesicles are 4-5 mm, superficial, flattened. Symptoms associated with days 8-11include skin vesicles that are soft, flat and velvety, some with huge confluent bullae (like Stevens Johnson Syndrome). Symptoms associated with days 12-13 are: massive exfoliation (like a severe burn), keratitis leading to blindness, hemoptysis, uterine hemorrhage, an absence of platelets, neutropenia and lymphocytosis. Symptoms connected with third week involve: an inability to eat or drink, from severe throat pain with swallowing, huge areas of skin peeling off with even slight pressure: Widespread stripping of epithelium, “mortification” from tissue destruction, fetid odor. Other third week symptoms include bacterial sepsis and death (70%) from severe tissue destruction.

Hemorrhagic Smallpox

The most extreme type is flat hemorrhagic smallpox, in which the skin does not blister but remains smooth. It darkens until it can look charred, and it can slip off the body in sheets. (15:42) It occurs in about 3 to 25% of fatal cases. (15:42) Hemorrhagic smallpox is more common in teenagers, (15:42) and pregnant women appear to be unusually susceptible. (9:4)

Illness usually begins with a somewhat shorter incubation period and is characterized by a severely prostrating prodromal illness with high fever and head, back and abdominal pain. (9:4) “Intense prostration” with severe headache and backache. The prodrome, which can be prolonged, is characterized by fever, intense headache and backache, restlessness, a dusky flush or sometimes pallor of the face, extreme prostration and toxicity. (22:V1:14) Patients tend to be alert, but apprehensive. There is little or no remission of fever throughout the illness. Hemorrhagic manifestations can occur early or late in the course of the illness. (22:V1:14) In those cases in which it occurs early in the illness, the hemorrhagic manifestations appear on the second or third day as subconjunctival bleeding, bleeding from the mouth or gums, and other mucous membranes, petechia in the skin, epistaxis, and hematuria. (22:V1:14) These patients will have a quickly progressive disease course and often develop signs and symptoms of inflammatory shock. (22:V3:47) Death often occurs suddenly between the fifth and seventh days of illness, when only a few insignificant maculopapular cutaneous lesions are present. (22:V3:44)

Hemorrhagic manifestations, when they do develop, the rash it may not look at all like smallpox. (22:V1:46) It can appear as blotchy, blanching erythema on arms and trunk. Petechiae and hemorrhage in the mouth and on the skin can occur. The patients may develop superficial vesicles. Acute Respiratory Distress Syndrome is also possible. Blood counts may suggest leukemia, and include myeloblasts.

Variola Sine Eruptione

It is possible to be infected with smallpox, but not erupt in the rash. Patients experience the symptoms common to the prodrome, but it is usually of short duration. In order to diagnose this infection, laboratory workup is required. (22:V3:24) Symptoms of this unusual type of smallpox include: a fever of 39¾C, headache, backache, recovered in 48 hours.

Variola Minor (alastrim)

Variola minor, also called a varioloid rash (15:41), was first described in South Africa in 1904 and in the United States in 1913. It was endemic in some countries in Europe and North and South America, and in many parts of Africa. It is a less severe disease, with a case fatality rate of 1% or less. (9:3) The last naturally occurring case occurred in Somalia in October 1977. Recognized strains of variola minor include alastrim, kaffir, and amass. 

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