DEFINITION
Monkeypox is a rare disease that is caused by infection with monkeypox virus. Monkeypox virus belongs to the Orthopoxvirus genus in the family Poxviridae. The Orthopoxvirus genus also includes variola virus (which causes smallpox), vaccinia virus (used in the smallpox vaccine), and cowpox virus.
Monkeypox was first discovered in 1958 when two outbreaks of a pox-like disease occurred in colonies of monkeys kept for research, hence the name ‘monkeypox.’ The first human case of monkeypox was recorded in 1970 in the Democratic Republic of the Congo (DRC) during a period of intensified effort to eliminate smallpox. Since then, monkeypox has been reported in people in several other central and western African countries: Cameroon, Central African Republic, Cote d’Ivoire, Democratic Republic of the Congo, Gabon, Liberia, Nigeria, Republic of the Congo, and Sierra Leone. The majority of infections are in Democratic Republic of the Congo.
Monkeypox cases in people have occurred outside of Africa linked to international travel or imported animals, including cases in the United States, as well as Israel, Singapore, and the United Kingdom.
The natural reservoir of monkeypox remains unknown. However, African rodents and non-human primates (like monkeys) may harbor the virus and infect people.
Symptoms
In humans, the symptoms of monkeypox are similar to but milder than the symptoms of smallpox. Monkeypox begins with fever, headache, muscle aches, and exhaustion. The main difference between symptoms of smallpox and monkeypox is that monkeypox causes lymph nodes to swell (lymphadenopathy) while smallpox does not. The incubation period (time from infection to symptoms) for monkeypox is usually 7−14 days but can range from 5−21 days.
The illness begins with:
Fever
Headache
Muscle aches
Backache
Swollen lymph nodes
Chills
Exhaustion
Within 1 to 3 days (sometimes longer) after the appearance of fever, the patient develops a rash, often beginning on the face then spreading to other parts of the body.
Lesions progress through the following stages before falling off:
Macules
Papules
Vesicles
Pustules
Scabs
The illness typically lasts for 2−4 weeks. In Africa, monkeypox has been shown to cause death in as many as 1 in 10 persons who contract the disease.
Transmission
Transmission of monkeypox virus occurs when a person comes into contact with the virus from an animal, human, or materials contaminated with the virus. The virus enters the body through broken skin (even if not visible), respiratory tract, or the mucous membranes (eyes, nose, or mouth). Animal-to-human transmission may occur by bite or scratch, bush meat preparation, direct contact with body fluids or lesion material, or indirect contact with lesion material, such as through contaminated bedding. Human-to-human transmission is thought to occur primarily through large respiratory droplets. Respiratory droplets generally cannot travel more than a few feet, so prolonged face-to-face contact is required. Other human-to-human methods of transmission include direct contact with body fluids or lesion material, and indirect contact with lesion material, such as through contaminated clothing or linens.
The reservoir host (main disease carrier) of monkeypox is still unknown although African rodents are suspected to play a part in transmission. The virus that causes monkeypox has only been recovered (isolated) twice from an animal in nature. In the first instance (1985), the virus was recovered from an apparently ill African rodent (rope squirrel) in the Equateur Region of the Democratic Republic of Congo. In the second (2012), the virus was recovered from a dead infant mangabey found in the Tai National Park, Cote d’Ivoire.
Prevention
There are number of measures that can be taken to prevent infection with monkeypox virus:
Avoid contact with animals that could harbor the virus (including animals that are sick or that have been found dead in areas where monkeypox occurs).
Avoid contact with any materials, such as bedding, that has been in contact with a sick animal.
Isolate infected patients from others who could be at risk for infection.
Practice good hand hygiene after contact with infected animals or humans. For example, washing your hands with soap and water or using an alcohol-based hand sanitizer.
Use personal protective equipment (PPE) when caring for patients.
JYNNEOSTM (also known as Imvamune or Imvanex) is an attenuated live virus vaccine which has been approved by the U.S. Food and Drug Administration for the prevention of monkeypox. The Advisory Committee on Immunization Practices (ACIP) is currently evaluating JYNNEOSTM for the protection of people at risk of occupational exposure to orthopoxviruses such as smallpox and monkeypox in a pre-event setting.
Treatment
At this time, there are no specific treatments available for monkeypox infection, but monkeypox outbreaks can be controlled.
Smallpox vaccine, cidofovir, ST-246, and vaccinia immune globulin (VIG) can be used to control a monkeypox outbreak. CDC guidance was developed using the best available information about the benefits and risks of smallpox vaccination and drug use for the prevention and management of monkeypox and other orthopoxvirus infections.
One vaccine, JYNNEOSTM (also known as Imvamune or Imvanex), has been licensed in the United States to prevent monkeypox and smallpox. Because monkeypox virus is closely related to the virus that causes smallpox, smallpox vaccine can also protect people from getting monkeypox. Past data from Africa suggests that smallpox vaccine is at least 85% effective in preventing monkeypox. The effectiveness of JYNNEOSTM against monkeypox was concluded from a clinical study on the immunogenicity of JYNNEOS and efficacy data from animal studies. Experts also believe that vaccination after a monkeypox exposure may help prevent the disease or make it less severe.
ACAM2000, which contains a live vaccinia virus, is licensed for immunization in people who are at least 18 years old and at high risk for smallpox infection. It can be used in people exposed to monkeypox if used under an expanded access investigational new drug protocol.
Smallpox vaccine is not currently available to the general public. In the event of another outbreak of monkeypox in the U.S., CDC will establish guidelines explaining who should be vaccinated. For more information about the smallpox vaccine please visit CDC’s Smallpox Vaccination Information for Health Professionals.
Components of a smallpox vaccination kit including the diluent, a vial of Dryvax® smallpox vaccine, and a bifurcated needle.
Smallpox vaccination kit.
Cidofovir and Brincidofovir (CMX001)
Data is not available on the effectiveness of Cidofovir and Brincidofovir in treating human cases of monkeypox. However, both have proven activity against poxviruses in in vitro and animal studies.
It is unknown whether or not a person with severe monkeypox infection will benefit from treatment with either antiviral, although their use may be considered in such instances. Brincidofovir may have an improved safety profile over Cidofovir. Serious renal toxicity or other adverse events have not been observed during treatment of cytomegalovirus infections with Brincidofovir as compared to treatment using Cidofovir.
Tecovirimat (ST-246)
Data is not available on the effectiveness of ST-246 in treating human cases of monkeypox.
Studies using a variety of animal species have shown that ST-246 is effective in treating orthopoxvirus-induced disease. Human clinical trials indicated the drug was safe and tolerable with only minor side effects.
Although currently stockpiled by the Strategic National Stockpile, use of ST-246 is administered under an IND.
Vaccinia Immune Globulin (VIG)
Data is not available on the effectiveness of VIG in treatment of monkeypox complications. Use of VIG is administered under an IND and has no proven benefit in the treatment of smallpox complications. It is unknown whether a person with severe monkeypox infection will benefit from treatment with VIG, however, its use may be considered in such instances.
VIG can be considered for prophylactic use in an exposed person with severe immunodeficiency in T-cell function for which smallpox vaccination following exposure to monkeypox is contraindicated.
