Bioterrorism Agents And Barrier Protection

Variola virus, Smallpox DEFINITION Smallpox is the most devastating infectious disease in the history of mankind. It has killed over 500 million people worldwide. The variola virus that emerged in human populations thousands of years ago causes smallpox.8 Literature dating from approximately 3700 BC in Egypt and 1100 BC in China suggests that the original sources of smallpox were in Asia and Africa. There is evidence that a major smallpox epidemic occurred at the end of the eighteenth Egyptian dynasty. Research from the mummy of Pharaoh Ramses V, who died in 1157 BC, indicates that he most likely died of smallpox. From ancient Egypt, traders spread the disease to India, and then to Europe during the Middle Ages. Spanish colonists brought smallpox to the United States in the fifteenth and sixteenth centuries. After an extensive and successful eradication program, the World Health Assembly (WHA) certified the global eradication of smallpox in 1980. There has not been a reported case of smallpox in over twenty years. Successful efforts to prevent the spread of smallpox through vaccination changed the course of history of Western medicine. Most people think that since smallpox was eradicated, it is no longer a threat. However, when smallpox was eradicated, two samples were maintained for research purposes. These samples were kept at the CDC and in a research facility in Russia. After the end of the Cold War, unemployed Soviet scientists went to work for terrorist organizations and rogue nations, taking their knowledge, equipment, and samples, including smallpox, with them.9 In the aftermath of the events of September and October 2001, there is heightened concern that the variola virus might be used as a bioterrorism agent.3 There are two forms of smallpox: Variola Major A severe and more common form of smallpox, with a more extensive rash and higher fever. There are four types of variola major smallpox: Ordinary: the most frequent form, accounting for 90% of all cases. Modified: a mild form occurring in persons previously vaccinated for smallpox. Flat: a very rare and fatal form. Hemorrhagic: a very rare and very fatal form. Variola Minor This is a much less severe and less common form of smallpox, with death rates of 1% or less. CLINICAL MANIFESTATIONS OF SMALLPOX Exposure to the virus is followed by an incubation period during which people do not have any symptoms and may feel fine. The incubation period averages about 12 to 14 days, with a range from 7 to 17 days. During this time people are not contagious and cannot spread the virus to others. Typically, a two-stage illness will follow. First is the Prodrome stage, lasting from 2 to 4 days. During this stage, the person will present with “flu-like” symptoms including fever, malaise, head and body aches, and sometimes vomiting. The fever is usually high, in the range of 101° to 104° Fahrenheit. During this stage the person may be contagious. They then move to the next stage of the disease, the Eruptive stage. A rash emerges first as small red spots on the tongue and in the mouth. These spots develop into sores that break open and spread large amounts of the virus into the mouth and throat.3,6 This is the most contagious phase of the disease. At this time, a rash will also appear on the skin, starting on the face and spreading to the arms and legs, and then to the hands and feet. The rash will usually spread to all parts of the body within 24 hours. The fever usually breaks as the skin rash appears and the patient may feel better. Around the third day of the skin rash, the rash becomes raised bumps. By the fourth day, the bumps fill with thick, opaque fluid and have a depression in the center that looks like a belly button (this is a major distinguishing characteristic of smallpox). Fever will rise again and stay high until scabs form over the bumps. The bumps will become pustules that are raised, round, and firm to the touch. The pustules then begin to form a crust and then scab over. The pustules and scab portion takes approximately 5 days, and the person remains very contagious during this time. At this time the scabs begin to fall off, leaving pitted scars. This takes another 6 to 7 days, and the person remains contagious. About 3 weeks after the rash first appeared, the scabs fall off and the person is no longer contagious. TRANSMISSION Humans are the only natural reservoirs of variola virus. Person-to-person transmission of smallpox occurs through aerosol droplets expelled from the oropharynx of infected persons, or by direct contact with an infected person. The virus can also be spread through contaminated bedding and clothing, and through direct contact with infected bodily fluids. It is not known to be transmitted by insects or animals. DIAGNOSIS Smallpox is most frequently misdiagnosed as varicella, or chickenpox, which is caused by the herpes virus. The most effective criteria for distinguishing the two infections is an examination of the following characteristics of the lesions: Time and Pattern of Appearance The most obvious distinction between smallpox and chickenpox is the manner in which the skin lesions appear. In chickenpox, the lesions occur in successive “crops.” It is possible to determine several different stages of lesion maturation and development at the same time. In smallpox, the lesions appear simultaneously. All lesions have the same maturation. Density and Location Chickenpox lesions tend to be denser over the trunk, while smallpox lesions are denser on the face and extremities. Smallpox is almost always seen on the palms and soles of the feet, which is unusual for chickenpox. Smallpox can be confirmed in the laboratory by electron microscopic examination of vesicular or pustule liquid or scabs. Definitive laboratory identification and characterization involves growth of the virus in the cell culture, and characterization of strains by use of biologic assays, including polymerase chain reaction, restriction fragment-length polymorphism analysis, and Enzyme-Linked Immunoabsorbent Assay (ELISA). Confirmation using these methods can be accomplished in a few hours. Notification of the local and state health departments is necessary. TREATMENT Currently, there are no known effective antivirals. Provide the patient supportive care and antibiotics for secondary infections. The discovery of a single suspected case of smallpox must be treated as an international health emergency and immediately brought to the attention of national officials through local and state health authorities. POST-EXPOSURE PROPHYLAXIS All contacts must be vaccinated within 3 to 5 days. Contacts include all household members, patients, staff, and visitors to the hospital at the same time as the smallpox case.7 Monitor all patient contacts for 17 days, and if one of the contacts starts showing signs of a fever, they should be isolated as soon as possible. Patients become infectious the day before the rash, so conduct a thorough history of all contacts the day before they broke out, and monitor all of those contacts. INFECTION CONTROL Standard Precautions are recommended. Standard Precautions Handwashing Wash hands immediately after gloves are removed, between patient contacts, and when otherwise indicated to avoid transfer of microorganisms to other patients or environments. Gloves Wear gloves when touching blood, bodily fluid, secretions, excretions, and contaminated items; put on clean gloves just before touching mucous membranes and nonintact skin. Change gloves between tasks and procedures on the same patient after contact with material that may contain a high concentration of microorganisms. Remove gloves promptly after use, before touching noncontaminated items and environmental surfaces, and before going to another patient.Wash hands immediately to avoid transfer of microorganisms to other patients or environments. Masks, eye protection, face shields Wear a standard surgical mask and eye protection or a face shield to protect mucous membranes of the eyes, nose, and mouth during procedures and activities that are likely to generate splashes or sprays. Airborne Precautions Place the patient in a private room with negative air-pressure ventilation. Use external air exhaust or high-efficiency particulate air filters if the air is recirculated.10,11 Keep the door to the room closed. N-95 respirator. Contact Precautions Place patient in a private room. Gloves should be worn when entering the room and removed before leaving the room. Hands should be washed with an antimicrobial agent or a waterless handwashing agent immediately after removing gloves. Gowns should be worn when entering the room if it is anticipated that clothing will have contact with the patient, environmental surfaces, or items in the room. The gown should be removed before leaving the patient’s room. Patient transport should be limited to essential purposes only. Noncritical patient-care equipment should be dedicated whenever possible.

Previous Page | Table of Contents | Next Page