Giuseppe
Emeritus
[Source: World Health Organization, Weekly Epidemiological Record, full PDF document: (LINK). Extract, edited.]
Monkeypox ? Facts Sheet (1)
Monkeypox is a viral zoonosis (that is, a virus transmitted to humans from animals), and symptoms in humans are similar to those that were seen in smallpox patients in the past.
However, smallpox was eradicated worldwide in 1980, but monkeypox still occurs sporadically in parts of Africa (Map 1).
Monkeypox is a member of the Orthopoxvirus genus in the Poxviridae family.
The virus was first identified by the State Serum Institute in Copenhagen, Denmark, in 1958 during an investigation into a pox-like disease occurring among monkeys.
Outbreaks
Monkeypox was first identified in humans in 1970 in the Democratic Republic of the Congo. Since then, the majority of cases have been reported in rural regions of the Congo Basin and western Africa, particularly in the Democratic Republic of the Congo. During 1996?1997, a major outbreak occurred in the Democratic Republic of the Congo. In the spring of 2003, monkeypox cases were confirmed in the Midwest of the United States, marking the first reported occurrence of the disease outside of the African continent. In 2007, monkeypox was reported in Unity, Sudan.
Transmission
Infections of index cases result from direct contact with the blood, bodily fluids or rashes of infected animals.
In Africa, human infections have been documented to have occurred through the handling of infected monkeys, Gambian rats or squirrels.
Secondary transmission occurs from human to human, resulting from close contact with infected respiratory tract excretions, with the skin lesions of an infected person or from recently contaminated objects. Transmission via respiratory droplets has also been documented.
Transmission may also occur through inoculation or via the placenta (known as congenital monkeypox). There is no evidence that person-to-person transmission alone can sustain monkeypox in the human population.
Signs and symptoms
The incubation period of monkeypox (that is, the interval from the time of infection to the onset of symptoms) varies from 6 days to 16 days.
The illness can be divided into 2 periods:
Some patients develop severe lymphadenopathy before the rash appears. The presence of lymphadenopathy can help identify the disease as monkeypox since it is not characteristic of either smallpox or chickenpox.
The symptoms of monkeypox usually last from 14 days to 21 days.
The case-fatality rate has varied widely among epidemics but has been <10% in documented cases.
Most fatalities occur in young children. In addition, children may be more susceptible to monkeypox as a result of the termination of regular smallpox vaccination following worldwide eradication of the disease.
Diagnosis
The differential diagnoses usually include smallpox, chickenpox, measles, bacterial skin infections, scabies, medicamentous allergies and syphilis.
Monkeypox can be diagnosed definitively only by laboratory testing. A number of different tests may be used:
There are no medicines to treat or vaccines available to prevent monkeypox, although vaccination against smallpox has proved to be 85% effective in preventing monkeypox.
Natural hosts of the virus
In Africa, monkeypox infection has been found in many animal species: rope squirrels, tree squirrels, Gambian rats, striped mice, doormice and primates. Doubts persist about the natural history of the virus, and further studies are needed to identify the exact reservoir of the monkeypox virus and how it is maintained in nature.
In the United States, the virus is thought to have been transmitted from African animals to a number of susceptible non-African species (such as prairie dogs) with which they were co-housed.
Prevention
Preventing the spread of the virus by controlling animal trade
Restricting or banning the movement of small African mammals and monkeys may be effective in slowing the spread of the virus outside Africa.
Captive animals should not be inoculated against smallpox. Instead, infected animals should be isolated from other animals and placed into immediate quarantine.
Any animals that might have come into contact with an infected animal should be quarantined and observed for monkeypox symptoms for 30 days.
Reducing the risk of infection in people
During monkeypox outbreaks, close contact with other patients is the most significant risk factor for infection with the monkeypox virus. In the absence of specific treatment and a vaccine, the only way to reduce infection in people is by raising awareness of the risk factors, and educating people about the measures they can take to reduce their exposure to the virus.
Educational public-health messages should focus on:
Health-care workers caring for patients with suspected or confirmed infection with the monkeypox virus, or handling specimens from them, should implement standard infection-control precautions.
Health-care workers and those treating or exposed to patients with monkeypox or their samples should consider being immunized against smallpox. However, the smallpox vaccination should not be administered to people with compromised immune systems.
Samples taken from people and animals suspected to be infected with the monkeypox virus should be handled by trained staff working in suitably equipped laboratories.
WHO?s response
WHO?s country offices are supporting surveillance and outbreak-response activities in affected countries.
(1) This WHO fact sheet was last updated in February 2011.
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Monkeypox ? Facts Sheet (1)
Monkeypox is a viral zoonosis (that is, a virus transmitted to humans from animals), and symptoms in humans are similar to those that were seen in smallpox patients in the past.
However, smallpox was eradicated worldwide in 1980, but monkeypox still occurs sporadically in parts of Africa (Map 1).
Monkeypox is a member of the Orthopoxvirus genus in the Poxviridae family.
The virus was first identified by the State Serum Institute in Copenhagen, Denmark, in 1958 during an investigation into a pox-like disease occurring among monkeys.
Outbreaks
Monkeypox was first identified in humans in 1970 in the Democratic Republic of the Congo. Since then, the majority of cases have been reported in rural regions of the Congo Basin and western Africa, particularly in the Democratic Republic of the Congo. During 1996?1997, a major outbreak occurred in the Democratic Republic of the Congo. In the spring of 2003, monkeypox cases were confirmed in the Midwest of the United States, marking the first reported occurrence of the disease outside of the African continent. In 2007, monkeypox was reported in Unity, Sudan.
Transmission
Infections of index cases result from direct contact with the blood, bodily fluids or rashes of infected animals.
In Africa, human infections have been documented to have occurred through the handling of infected monkeys, Gambian rats or squirrels.
Secondary transmission occurs from human to human, resulting from close contact with infected respiratory tract excretions, with the skin lesions of an infected person or from recently contaminated objects. Transmission via respiratory droplets has also been documented.
Transmission may also occur through inoculation or via the placenta (known as congenital monkeypox). There is no evidence that person-to-person transmission alone can sustain monkeypox in the human population.
Signs and symptoms
The incubation period of monkeypox (that is, the interval from the time of infection to the onset of symptoms) varies from 6 days to 16 days.
The illness can be divided into 2 periods:
- the invasive period (lasting 0?5 days), which is characterized by fever, intense headache, lymphadenopathy (swelling of the lymph nodes), back pain, myalgia (muscle ache) and an intense asthenia (lack of energy);
- the skin-eruption period, during which the various stages of the eruption appear on the face (in 95% of cases), on the palms of the hands and soles of the feet (in 75% of cases), and on the body nearly simultaneously. During approximately 10 days, the rash evolves from maculopapules (lesions with a flat base) to vesicles (small fluid-filled blisters) to pustules, over which crusts then form. It may take up to 3 weeks for the crusts to disappear completely.
Some patients develop severe lymphadenopathy before the rash appears. The presence of lymphadenopathy can help identify the disease as monkeypox since it is not characteristic of either smallpox or chickenpox.
The symptoms of monkeypox usually last from 14 days to 21 days.
The case-fatality rate has varied widely among epidemics but has been <10% in documented cases.
Most fatalities occur in young children. In addition, children may be more susceptible to monkeypox as a result of the termination of regular smallpox vaccination following worldwide eradication of the disease.
Diagnosis
The differential diagnoses usually include smallpox, chickenpox, measles, bacterial skin infections, scabies, medicamentous allergies and syphilis.
Monkeypox can be diagnosed definitively only by laboratory testing. A number of different tests may be used:
- enzyme-linked immunosorbent assay (ELISA);
- antigen-detection tests;
- polymerase chain reaction (PCR) assay;
- virus isolation by cell culture.
There are no medicines to treat or vaccines available to prevent monkeypox, although vaccination against smallpox has proved to be 85% effective in preventing monkeypox.
Natural hosts of the virus
In Africa, monkeypox infection has been found in many animal species: rope squirrels, tree squirrels, Gambian rats, striped mice, doormice and primates. Doubts persist about the natural history of the virus, and further studies are needed to identify the exact reservoir of the monkeypox virus and how it is maintained in nature.
In the United States, the virus is thought to have been transmitted from African animals to a number of susceptible non-African species (such as prairie dogs) with which they were co-housed.
Prevention
Preventing the spread of the virus by controlling animal trade
Restricting or banning the movement of small African mammals and monkeys may be effective in slowing the spread of the virus outside Africa.
Captive animals should not be inoculated against smallpox. Instead, infected animals should be isolated from other animals and placed into immediate quarantine.
Any animals that might have come into contact with an infected animal should be quarantined and observed for monkeypox symptoms for 30 days.
Reducing the risk of infection in people
During monkeypox outbreaks, close contact with other patients is the most significant risk factor for infection with the monkeypox virus. In the absence of specific treatment and a vaccine, the only way to reduce infection in people is by raising awareness of the risk factors, and educating people about the measures they can take to reduce their exposure to the virus.
Educational public-health messages should focus on:
- reducing the risk of human-to-human transmission.
- Close physical contact with people infected with the monkeypox virus should be avoided.
- Gloves and protective equipment should be worn when taking care of ill people. Regular handwashing should be carried out after caring for or visiting sick people;
- reducing the risk of animal-to-human transmission.
- Efforts to prevent transmission in endemic regions should emphasize that all animal products (such as blood or meat) must be thoroughly cooked before being eaten. Gloves and other appropriate protective clothing should be worn while handling sick animals or their infected tissues, and during slaughter.
Health-care workers caring for patients with suspected or confirmed infection with the monkeypox virus, or handling specimens from them, should implement standard infection-control precautions.
Health-care workers and those treating or exposed to patients with monkeypox or their samples should consider being immunized against smallpox. However, the smallpox vaccination should not be administered to people with compromised immune systems.
Samples taken from people and animals suspected to be infected with the monkeypox virus should be handled by trained staff working in suitably equipped laboratories.
WHO?s response
WHO?s country offices are supporting surveillance and outbreak-response activities in affected countries.
(1) This WHO fact sheet was last updated in February 2011.
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