This island was a testing site for the Soviet bioweapons program. The outbreak was contained due to a massive public health response of vaccinations, decontamination and quarantine measures. Smallpox is a deadly and highly contagious disease caused by Variola major , a double-stranded DNA orthopox virus. It has been a major cause of death throughout history, killing more than million people in the 20th century.
For comparison, the current population of the United States is a little over million. Transmission occurs mainly through the inhalation of respiratory droplets formed by coughing and sneezing from infected individuals. It can also spread through fomites, which are scab contaminated materials such as bedding and clothing. Because smallpox only infects humans and cannot survive for more than a few months outside its host under the most optimal conditions, it was a good candidate for disease eradication by the World Health Organization WHO.
Stocks of the virus are kept by the United States and Russia for research purposes. Variola major is considered an effective bioweapon for a number of reasons. First, it is highly contagious; a single uncontrolled case would likely infect more people, exponentially spreading the disease. It also has a low infectious dose and a relatively high fatality rate. In addition, V. The majority of the global population is unvaccinated against smallpox, making.
This was highly effective, but could cause later neurological sequealae, and so the standard vaccine that was used to eradicate smallpox was the vaccinia virus. Vaccinia virus either had its origins from a recombinational event between the cowpox or variola virus through serial passage or could be the representative of a long-since extinct virus. Arguably the greatest triumph of medicine was the eradication of this disease through extensive vaccination programs and surveillance methods.
Now only laboratory workers that handle the variola virus continue to be vaccinated. There was no treatment in wide use for smallpox. For most people infected, they just had to wait for the disease to run its course.
In the s, the Soviet Union developed variola as an aerosol biological weapon and produced tons of virus-laden material annually intended for intercontinental ballistic missiles. Since routine smallpox immunization ceased in the United States in and in all other countries by , the global population is extremely vulnerable to the disease. Most of the world's population has never been vaccinated or was vaccinated so long ago that immunity to smallpox has waned. Because there are no symptoms at the time of exposure, a covert release of variola may not be detected until sick people begin showing up at doctor's offices and hospitals.
Smallpox spreads from person to person by respiratory droplets or direct contact with body fluids. Contaminated clothing or bedding may also transmit the virus.
Animals and insects are not known to carry or spread the virus to humans. The incubation period for smallpox is 7 to 17 days. Individuals diagnosed with or suspected of having smallpox should be isolated to prevent the spread of disease. Household and other face-to-face contacts of patients who have, or are suspected of having, smallpox should be vaccinated and placed under surveillance.
For smallpox patients in the hospital, airborne precautions see CDC Isolation Precautions Guidelines should be followed, and all hospital personnel should be vaccinated. Diagnosis of smallpox is based on clinical presentation of symptoms in the patient and is confirmed by laboratory testing. Symptoms most often begin 12 to 14 days after infection, and include high fever, severe malaise, and exhaustion with headache and backache.
A rash of small, pink bumps appears in the mouth, on the face and forearms, and then spreads to the trunk of the body and legs, including the palms and soles.
Within 1 to 2 days, the rash becomes first fluid-filled and then pus-filled. Lesions are round, hard and deep; they begin to crust over on day 8 or 9.
Survivors are often left disfigured, with permanent scars on the face. Source: CDC. Complications of smallpox include bacterial superinfections of the skin and organs, pneumonia, sepsis, arthritis, keratitis, and encephalitis.
In contrast to smallpox, chickenpox the disease with which it is most likely to be confused is associated with a milder prodromal illness and a rash that is more superficial, usually starts on the trunk and spreads centripetally, has lesions in different stages of evolution, and rarely appears on the palms or soles.
Smallpox is caused by 1 of 2 closely related strains: variola major and variola minor. A severe prodrome lasts 3 to 4 days, followed by prolonged high fever and severe symptoms of toxemia.
The enanthem on the tongue and palate is extensive. Skin lesions mature relatively slowly; by days 7 to 8, vesicles are flat, and nearly flush with the skin surface. Unlike ordinary-type smallpox, vesicles contain little fluid, are soft, and may contain hemorrhage. Death is often associated with pneumonia. This form is difficult to diagnose clinically unless there is an ongoing smallpox epidemic or known exposure.
Diagnosis is typically by biopsy. The prodrome is severe and prolonged, with toxemia and prostration. There is extensive bleeding into the skin, nasal and oral mucous membranes, and gastrointestinal tract.
This form usually develops in adults, equally among the vaccinated and unvaccinated, and is usually fatal. Platelets and clotting factors are affected, denoting some similarity with disseminated intravascular coagulation.
Hemorrhagic smallpox has two clinical forms, early and late. Early: the prodrome is characterized by petechial hemorrhages in the skin or mucous membranes. Subconjunctival bleeding may cause the sclera to appear deep red. There may be hemorrhage in the retina, spleen, kidney, serosa, muscle, and other organs. Late: hemorrhages appear in the early period of a typical smallpox exanthem, but the lesions remain relatively flat and do not progress beyond the vesicular stage.
Death occurs by day Men and women are equally susceptible. Synonyms include alastrim, cottonpox, milkpox, whitepox, and Cuban itch. Minor smallpox is similar to two forms of major smallpox: modified, and ordinary with discrete lesions. Smallpox is presumptively diagnosed on clinical features and then confirmed by laboratory tests conducted at the US CDC or other high-containment laboratories.
The algorithm is especially helpful in differentiating smallpox from varicella Figure 8. Chart 1: symptoms of acute generalized vesiculo-pustular rash, and categories of risk for smallpox.
Criteria: 1 No febrile prodrome, or 2 febrile prodrome and fewer than 4 minor smallpox criteria. E-mail: [email protected]. Smallpox can be isolated from clinical specimens when placed into culture with any one of several common cultured cell lines.
For a HIGH risk case, clinical specimens, which may include pustule contents optimal ; tonsillar swab, urine, skin biopsy or blood should be collected, if possible, by someone recently vaccinated for smallpox within the past 5 years.
Sampling, handling and transport guidelines vary. The receiving laboratory must have advanced bio-containment facilities. Electron microscopy: orthopoxviruses, including smallpox, produce oval or brick-shaped virions Figure Histology: poxviruses, including smallpox, show multilocular intraepidermal vesicles with ballooning degeneration, cell necrosis and serous exudate.
Characteristic cytoplasmic eosinophilic inclusion bodies, the most important being Guarnieri bodies B type inclusions , represent sites of virus replication. Guarnieri bodies are not produced by herpesviruses. Conditions most likely to be confused with smallpox include those with acute onset of fever and disseminated vesicular or pustular rash Figure 12—Tables 1 and 2.
Monkeypox, described as a human disease in in the Congo, is endemic in West Africa Figure It was first reported in the United States in , when imported Ghana giant rats transmitted the disease to prairie dogs and humans. Reservoirs include rodents African squirrels and possibly monkeys.
Monkeypox is transmitted by aerosol droplets or direct skin-to-skin contact and is less infectious and less lethal than smallpox. Smallpox vaccination may prevent monkeypox.
Smallpox virus is highly contagious, but less so than measles and influenza. The most common form of transmission is inhalation of airborne virus droplets shed from the nasopharyngeal mucosa of an infected person. Smallpox can also be transmitted by direct contact with infected body fluids or contaminated objects such as bedding or clothing. Rarely, smallpox has been spread by virus carried in the air in enclosed settings such as buildings, buses, and trains.
Transmission from one person to another generally requires direct within 6 feet and prolonged estimated 1 to 3 hours face-to-face contact. Family members and other close household contacts of symptomatic rash smallpox patients, and health care workers are most at risk. Among family members, the very young, pregnant women and elderly are most susceptible.
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