Monkeypox
Monkeypox
Disease History, Characteristics, and Transmission
Introduction
Monkeypox is an infectious viral disease that is very similar to smallpox but milder. There is very low prevalence of this disease, with almost all cases occurring in west and central Africa. The first outbreak in the United States occurred in 2003. This disease causes smallpox-like symptoms, including fever, headache, muscle aches, backache, exhaustion, and discomfort in addition to a papular rash over the body. One symptom common in monkeypox but not smallpox is the swelling of the lymph nodes.
Monkeypox is a zoonosis, a disease humans can contract from an infected animal. It is usually contracted via an animal bite, or by coming into contact with the bodily fluids of infected animals. There is no treatment for monkeypox, but fatality rates are low, with most patients recovering in 2–4 weeks. Monkeypox can be prevented by controlling the transmission of the disease from animals to humans. This involves reporting diseased animals, and taking appropriate action to prevent transfer of the virus to humans.
Disease History, Characteristics, and Transmission
Monkeypox is a rare disease caused by the monkeypox virus. This virus belongs to the orthopoxvirus group of viruses, which also includes smallpox and cowpox. Monkeypox was first discovered in 1958. It was first identified in laboratory monkeys and later in rodents. The first human case of monkeypox was reported in 1970.
Monkeypox is found in many animals including monkeys, mice, rats, rabbits, and squirrels. All mammals are thought to be susceptible to this virus. Humans become infected with monkeypox when they come into direct contact with an infected animal's bodily fluids— either through an animal bite or by touching its lesions. This virus can also be transmitted by airborne droplets from the respiratory tract. Therefore, face to face contact between an infected animal and a human also can spread this virus. Contact with contaminated items, such as bed sheets, can also spread the disease.
Monkeypox is a milder version of smallpox, presenting similar, although less severe, symptoms. Approximately 12 days after infection with the monkeypox virus, a person will develop an illness characterized by fever, headache, muscle aches, backache, exhaustion, and discomfort. Unlike smallpox, monkeypox also causes the lymph nodes to swell. A few days after these initial symptoms, a papular rash (raised bumps on the skin) begins to form. This rash usually develops first on the face before spreading across the body. The bumps develop, crust over, and finally fall off. The infection usually lasts 2–4 weeks. Between 1% and 10% of the people in Africa who contract monkeypox will die of the disease. No monkeypox fatalities have been reported outside of Africa.
Scope and Distribution
Monkeypox was first found in Africa. Most cases of monkeypox occur in central and western Africa, particularly in Zaire, and the countries in which it occurs are characterized by tropical rainforest. There is a low prevalence of the disease. Between 1970 and 1986, only 400 cases worldwide were reported by the World Health Organization.
In 2003, the first ever cases of monkeypox occurred in the United States. Of at least 79 reports of monkeypox, 29 were confirmed as true cases of monkeypox. It is argued that the virus was transmitted to humans by tame prairie dogs that were earlier in contact with infected Gambian rats from Africa. The tame prairie dogs probably contracted the virus from the Gambian rats.
Although the virus is similar to smallpox, which devastated populations prior to its eradication, monkeypox is not as transmissible as smallpox. While smallpox spread rapidly from person to person, only one-third of monkeypox cases arise in this way.
The people most at risk of developing monkeypox are those exposed to infected animals or infected patients. This includes investigators of current monkeypox outbreaks, veterinarians, health care workers, laboratory workers, and friends or family of monkeypox patients.
Treatment and Prevention
There is no safe, specific treatment for monkeypox. However, a good health care system, including adequate supportive care for symptoms, as well as good nutrition, aids recovery. The illness normally lasts 2–4 weeks and a person is no longer infectious when the rash lesions are crusted. No fatalities have been reported outside of Africa. However, within rural African regions, where health care is generally poor, monkeypox fatalities may reach 10% of reported cases.
There is no vaccination against monkeypox, although the smallpox vaccination has been found to be effective against monkeypox. However, the CDC does not recommend widespread smallpox vaccination. Instead, use of the vaccine is recommended only for high risk individuals, such as those caring for monkeypox patients, or people who have been in contact with infected animals and are at risk of becoming infected. Vaccination after exposure to the virus has been found to help prevent or reduce the severity of infection. However, vaccination should be avoided in patients with weakened immune systems or patients with life-threatening allergies to the smallpox vaccine and its ingredients, since the smallpox vaccine could be more harmful than the monkeypox virus in these cases.
In order to prevent spread of this disease, infected animals are separated from human populations as soon as possible. These animals are reported to the health department, and appropriate action is taken to keep the animal from transmitting the disease. As contact with fomites (contaminated surfaces such as clothing) and bedding can also result in transmission of the disease, these items must be washed with hot water and detergent to remove the virus.
WORDS TO KNOW
CHAIN OF TRANSMISSION: Chain of transmission refers to the route by which an infection is spread from its source to susceptible host. An example of a chain of transmission is the spread of malaria from an infected animal to humans via mosquitoes.
FOMITE: A fomite is an object or a surface to which an infectious microorganism such as bacteria or viruses can adhere and be transmitted. Transmission is often by touch.
ENDEMIC: Present in a particular area or among a particular group of people.
PAPULAR: A papule is a small, solid bump on the skin; papular means pertaining to or resembling a papule.
ZOONOSES: Zoonoses are diseases of microbiological origin that can be transmitted from animals to people. The causes of the diseases can be bacteria, viruses, parasites, and fungi.
Impacts and Issues
Monkeypox is not a widespread disease. While low mortality outbreaks occur in Africa, few outbreaks have been reported outside of African countries. Prior to 2003, monkeypox had not appeared in the United States and was not considered a threat. Since 2003, there has been one outbreak of monkeypox in the United States and, although the disease was contained, it is now considered a possible threat for United States citizens.
The outbreak in the United States included at least 29 confirmed cases of monkeypox. However, no deaths occurred due to this disease. The effect of this disease on victims in the United States was noticeably milder than its effect on African populations. A better national health care network is thought to have resulted in a more efficient and thus more effective containment of the disease. This health care network includes better nutrition, access to good supportive care, and availability of a vaccine.
IN CONTEXT: REAL-WORLD RISKS
The Centers for Disease Control and Prevention (CDC) states that “past data from Africa suggests that the smallpox vaccine is at least 85% effective in preventing monkeypox.” CDC states that: “for most persons who have been exposed to monkeypox, the risks from monkeypox disease are greater than the risks from the smallpox vaccine.”
“Studies of monkeypox in West Africa—where people live in remote areas and are medically underserved—showed that the disease killed 1%to 10% of people infected. In contrast, most people who get the smallpox vaccine have only expected minor reactions, like mild fever, tiredness, swollen glands, and redness and itching at the place where the vaccine is given. However the smallpox vaccine does have more serious risks too. Based on past experience, it is estimated that between 1 and 2 people out of every 1 million people vaccinated will die as a result of life-threatening reactions to the vaccine.”
SOURCE: Centers for Disease Control and Prevention
Future outbreaks in the United States and in other countries outside of Africa are still possible. However, not only are the chances of transmission throughout a population low, but it is unlikely that a chain of transmission would be sustained within a human community.
There has been some debate within the United States over the potential for monkeypox to be used by terrorists as a biological weapon. However, the efficient containment of this disease during the 2003 outbreak, coupled with the low likelihood that this disease would spread rapidly through the population, significantly reduces its risk as a bioweapon.
See AlsoBioterrorism; Smallpox; Smallpox Eradication and Storage; Viral Disease; Zoonoses.
BIBLIOGRAPHY
Periodicals
Huhn, G.D., et al. “Monkeypox in the Western
Hemisphere.” New England Journal of Medicine 350 (April 22, 2004): 1790–1791.
Web Sites
Centers for Disease Control and Prevention. “Questions and Answers about Monkeypox.” November 4, 2003. <http://www.cdc.gov/ncidod/monkeypox/qa.htm> (accessed March 6, 2007).
Illinois Department of Public Health. “Monkeypox.” <http://www.idph.state.il.us/health/infect/monkeypox.htm> (accessed March 6, 2007).
Stanford University. “Monkeypox.” Winter 2000. <http://www.stanford.edu/group/virus/pox/2000/monkeypox_virus.html> (accessed March 6, 2007).
University of Alabama. “History of Monkeypox.” May
25, 2005. <http://www.bioterrorism.uab.edu/EI/monkeypox/history.html> (accessed March 6, 2007).