Recent Outbreak of Monkeypox Virus in several countries: Overview of the Disease
Monkeypox cases have been reported in several countries in Africa such as Congo and Pakistan recently. The World Health Organization (WHO) announced on 14 August 2024 that it declared MPox a ‘public health emergency of international concern.
Monkeypox is a viral zoonosis (a virus transmitted to humans from animals) with symptoms very similar to those seen in the past in smallpox patients, although it is clinically less severe. Monkeypox virus is an enveloped double-stranded DNA virus that belongs to the Orthopoxvirus genus of the Poxviridae family.
The natural reservoir of monkeypox remains unknown. However, African rodents and non-human primates (like monkeys) may harbor the virus and infect people.
Monkeypox virus is transmitted from one person to another by close contact with lesions, body fluids, respiratory droplets and contaminated materials such as bedding.
While close physical contact is a well-known risk factor for transmission, it is unclear at this time if monkeypox can be transmitted specifically through sexual transmission routes.
Signs and symptoms
Monkeypox is usually a self-limited disease with symptoms lasting from 2 to 4 weeks. Severe cases can occur. Recently, the case fatality ratio has been around 3-6%.
The Incubation period (interval from infection to onset of symptoms) of monkeypox is usually from 7 to 14 days but can range from 5 to 21 days.
The Prodrome period (lasts between 0-5 days) is characterized by fever, intense headache, lymphadenopathy (swelling of the lymph nodes), back pain, myalgia (muscle aches) and intense asthenia (lack of energy).
Lymphadenopathy is a distinctive feature of monkeypox compared to other diseases that may initially appear similar (chickenpox, measles, smallpox).
The Eruptive period (skin eruption/rash) usually begins within 1-3 days of the appearance of fever. The rash tends to be more concentrated on the face and extremities rather than on the trunk. It affects the face (in 95% of cases), and palms of the hands and soles of the feet (in 75% of cases). Also affected are oral mucous membranes (in 70% of cases), genitalia (30%), and conjunctivae (20%), as well as the cornea.
The rash evolves sequentially from macules (lesions with a flat base) to papules (slightly raised firm lesions), vesicles (lesions filled with clear fluid), pustules (lesions filled with yellowish fluid), and crusts/scabs which dry up and fall off.
The number of lesions varies from a few to several thousand. In severe cases, lesions can coalesce until large sections of skin slough off.
Figure. Images of individual monkeypox lesions
Diagnosis
A definite diagnosis of monkeypox requires assessment by a health professional and specific testing in a specialist laboratory.
The clinical differential diagnosis that must be considered includes other rash illnesses, such as chickenpox, measles, bacterial skin infections, scabies, syphilis, and medication-associated allergies.
Lymphadenopathy during the prodromal stage of illness can be a clinical feature to distinguish monkeypox from chickenpox or smallpox.
Polymerase chain reaction (PCR) is the preferred laboratory test given its accuracy and sensitivity. For this, optimal diagnostic samples for monkeypox are from skin lesions – the roof or fluid from vesicles and pustules, and dry crusts. Where feasible, the biopsy is an option.
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Clinical care for monkeypox should be fully optimized to alleviate symptoms, manage complications and prevent long-term sequelae.
Patients should be offered fluids and food to maintain adequate nutritional status. Secondary bacterial infections should be treated as indicated.
Currently, there is no proven, safe treatment for monkeypox virus infection. For purposes of controlling a monkeypox outbreak, Smallpox vaccine, Antivirals (cidofovir), and Vaccinia immune globulin (VIG) can be used.
An antiviral agent known as Tecovirimat that was developed for smallpox was licensed by the European Medical Association (EMA) for monkeypox in 2022 based on data in animal and human studies. It is not yet widely available.
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.
Vaccination
Vaccination against smallpox was demonstrated through several observational studies to be about 85% effective in preventing monkeypox. Thus, prior smallpox vaccination may result in milder illness.
A still newer vaccine based on a modified attenuated vaccinia virus (Ankara strain) was approved for the prevention of monkeypox in 2019. This is a two-dose vaccine for which availability remains limited.
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.
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