Smallpox
A highly infectious, serious viral disease causing a skin rash and flu-like symptoms that has been totally eradicated throughout the world since 1980. The last naturally acquired case of smallpox occurred in Somalia in 1977, and the last cases of smallpox (from lab exposure) occurred in 1978. In May 1980 the World Health Assembly certified that the world was free of naturally occurring smallpox. However, the threat of smallpox has reemerged as a potential terroristic threat since the attack on the World Trade Center in New York City on September 11, 2001.
In the United States vaccination programs and quarantine regulations meant that by the 1960s the risk for importing smallpox had been reduced. As a result, recommendations for routine smallpox vaccination were rescinded in 1971. In 1976 the recommendation for routine smallpox vaccination of health-care workers was also discontinued. In 1982 the only active licensed producer of vaccinia vaccine in the United States discontinued production for general use, and in 1983 distribution to the civilian population was discontinued. Since January 1982 smallpox vaccination has not been required for international travelers, and International Certificates of Vaccination forms no longer include a space to record smallpox vaccination.
In the United States routine vaccination against smallpox ended in 1972. The level of immunity among vaccinated Americans is uncertain, so these people are assumed to be susceptible. Most estimates suggest immunity from the vaccination lasts only three to five years, which means that nearly the entire U.S. population has only partial immunity at best. Approximately half of the U.S. population has never been vaccinated.
In 1992 the government formed volunteer Smallpox Response Teams who can provide critical services to citizens in the event of a smallpox attack. To ensure that the teams can mobilize immediately in an emergency, health-care workers and other critical personnel were asked to volunteer to receive the smallpox vaccine. Although the United States currently has enough vaccine to vaccinate every single person in the country in an emergency, the federal government does not recommend vaccination for the general public because of both the possibility of side effects and the low level of threat. However, the Department of Defense vaccinates certain military and civilian personnel deployed in high threat areas, along with some personnel assigned to certain overseas embassies.
In addition, the government is preparing to make unlicensed vaccine available to those adult members of the general public without medical contraindications who insist on being vaccinated. Immunity can be boosted effectively with a single revaccination, and prior infection with the disease grants lifelong immunity.
The U.S. Centers for Disease Control (CDC) maintains an emergency supply of vaccine that can be released if necessary, since post-exposure vaccination is also effective in preventing the disease. In 2000 the CDC awarded a contract to a vaccine manufacturer to produce additional doses of smallpox vaccine in case of a bioterrorism attack. In the event of an outbreak, the CDC has clear guidelines to provide vaccine swiftly to people exposed to this disease. The vaccine is securely stored for use in the case of an outbreak.
Symptoms
The incubation period before symptoms appear ranges between seven and 17 days after exposure. Initial symptoms include high fever, fatigue, and head and back aches. A characteristic rash of flat red lesions, most prominent on the face, arms, and legs, follows in two to three days. Lesions become filled with pus after a few days, and then begin to crust early in the second week. Scabs develop, separate, and then fall off after about three to four weeks. Most patients with smallpox recover, but death may occur in up to 30 percent of cases.
In most cases, smallpox is spread from one person to another by infected saliva droplets that expose a susceptible person having face-to-face contact with the ill person. People with smallpox are most infectious during the first week of illness, because that is when the largest amount of virus is present in saliva. However, some risk of transmission lasts until all scabs have fallen off. Contaminated clothing or bed linen could also spread the virus. Special precautions need to be taken to ensure that all bedding and clothing of patients are cleaned appropriately with bleach and hot water. Disinfectants such as bleach and quaternary ammonia can be used for cleaning contaminated surfaces.
Vaccine
Smallpox vaccine does not contain smallpox virus but another live virus called vaccinia virus, which is related to smallpox. Vaccination provides immunity against infection from smallpox virus. If the vaccine is given within four days after exposure to smallpox, it can lessen the severity of illness or even prevent it. In addition to the stock of smallpox vaccine in the United States, an additional 50 million to 100 million doses are estimated to exist worldwide, and the World Health Organization (WHO) recommends that countries with stocks of smallpox vaccine maintain these stocks.
Side Effects
Side effects from successful vaccination include tenderness, redness, swelling, and a lesion at the vaccination site. In addition, the vaccination may cause fever for a few days and the lymph nodes in the vaccinated arm may become enlarged and tender. These symptoms are more common in those receiving their first dose of vaccine than in those being revaccinated. The overall risks of serious complications of smallpox vaccination are low and occur more frequently in those receiving their first dose of vaccine and among young children.
The most frequent serious complications are encephalitis, progressive destruction of skin and other tissues at the vaccination site, and severe and destructive infection of skin affected already by eczema or other chronic skin disorder. Encephalitis occurs in about one in 300,000 doses in children.
Who Should Not Be Vaccinated
The vaccine is not recommended for those who have abnormalities of the immune system because the complication of progressive destruction of skin and other tissues at the vaccination site has occurred only among recipients in this group. The vaccine is also not recommended for recipients who have eczema or other chronic skin disorders because the complication of severe and destructive infection of skin has occurred only among these patients.
Treatment
There is no proven treatment for smallpox, but researchers are studying new antiviral drugs. Patients with smallpox are given supportive treatment including intravenous fluids, medicine to control fever or pain, and antibiotics for secondary bacterial infections.
In the United States vaccination programs and quarantine regulations meant that by the 1960s the risk for importing smallpox had been reduced. As a result, recommendations for routine smallpox vaccination were rescinded in 1971. In 1976 the recommendation for routine smallpox vaccination of health-care workers was also discontinued. In 1982 the only active licensed producer of vaccinia vaccine in the United States discontinued production for general use, and in 1983 distribution to the civilian population was discontinued. Since January 1982 smallpox vaccination has not been required for international travelers, and International Certificates of Vaccination forms no longer include a space to record smallpox vaccination.
In the United States routine vaccination against smallpox ended in 1972. The level of immunity among vaccinated Americans is uncertain, so these people are assumed to be susceptible. Most estimates suggest immunity from the vaccination lasts only three to five years, which means that nearly the entire U.S. population has only partial immunity at best. Approximately half of the U.S. population has never been vaccinated.
In 1992 the government formed volunteer Smallpox Response Teams who can provide critical services to citizens in the event of a smallpox attack. To ensure that the teams can mobilize immediately in an emergency, health-care workers and other critical personnel were asked to volunteer to receive the smallpox vaccine. Although the United States currently has enough vaccine to vaccinate every single person in the country in an emergency, the federal government does not recommend vaccination for the general public because of both the possibility of side effects and the low level of threat. However, the Department of Defense vaccinates certain military and civilian personnel deployed in high threat areas, along with some personnel assigned to certain overseas embassies.
In addition, the government is preparing to make unlicensed vaccine available to those adult members of the general public without medical contraindications who insist on being vaccinated. Immunity can be boosted effectively with a single revaccination, and prior infection with the disease grants lifelong immunity.
The U.S. Centers for Disease Control (CDC) maintains an emergency supply of vaccine that can be released if necessary, since post-exposure vaccination is also effective in preventing the disease. In 2000 the CDC awarded a contract to a vaccine manufacturer to produce additional doses of smallpox vaccine in case of a bioterrorism attack. In the event of an outbreak, the CDC has clear guidelines to provide vaccine swiftly to people exposed to this disease. The vaccine is securely stored for use in the case of an outbreak.
Symptoms
The incubation period before symptoms appear ranges between seven and 17 days after exposure. Initial symptoms include high fever, fatigue, and head and back aches. A characteristic rash of flat red lesions, most prominent on the face, arms, and legs, follows in two to three days. Lesions become filled with pus after a few days, and then begin to crust early in the second week. Scabs develop, separate, and then fall off after about three to four weeks. Most patients with smallpox recover, but death may occur in up to 30 percent of cases.
In most cases, smallpox is spread from one person to another by infected saliva droplets that expose a susceptible person having face-to-face contact with the ill person. People with smallpox are most infectious during the first week of illness, because that is when the largest amount of virus is present in saliva. However, some risk of transmission lasts until all scabs have fallen off. Contaminated clothing or bed linen could also spread the virus. Special precautions need to be taken to ensure that all bedding and clothing of patients are cleaned appropriately with bleach and hot water. Disinfectants such as bleach and quaternary ammonia can be used for cleaning contaminated surfaces.
Vaccine
Smallpox vaccine does not contain smallpox virus but another live virus called vaccinia virus, which is related to smallpox. Vaccination provides immunity against infection from smallpox virus. If the vaccine is given within four days after exposure to smallpox, it can lessen the severity of illness or even prevent it. In addition to the stock of smallpox vaccine in the United States, an additional 50 million to 100 million doses are estimated to exist worldwide, and the World Health Organization (WHO) recommends that countries with stocks of smallpox vaccine maintain these stocks.
Side Effects
Side effects from successful vaccination include tenderness, redness, swelling, and a lesion at the vaccination site. In addition, the vaccination may cause fever for a few days and the lymph nodes in the vaccinated arm may become enlarged and tender. These symptoms are more common in those receiving their first dose of vaccine than in those being revaccinated. The overall risks of serious complications of smallpox vaccination are low and occur more frequently in those receiving their first dose of vaccine and among young children.
The most frequent serious complications are encephalitis, progressive destruction of skin and other tissues at the vaccination site, and severe and destructive infection of skin affected already by eczema or other chronic skin disorder. Encephalitis occurs in about one in 300,000 doses in children.
Who Should Not Be Vaccinated
The vaccine is not recommended for those who have abnormalities of the immune system because the complication of progressive destruction of skin and other tissues at the vaccination site has occurred only among recipients in this group. The vaccine is also not recommended for recipients who have eczema or other chronic skin disorders because the complication of severe and destructive infection of skin has occurred only among these patients.
Treatment
There is no proven treatment for smallpox, but researchers are studying new antiviral drugs. Patients with smallpox are given supportive treatment including intravenous fluids, medicine to control fever or pain, and antibiotics for secondary bacterial infections.
