The rare viral infection, monkeypox, was reported in Singapore in May 2019. This infection is transmitted from animals to humans.

It was discovered in 1958 when there were two outbreaks of a pox-like disease in monkeys kept for research, hence the name “monkeypox”.

The first human case of monkeypox occurred in the Democratic Republic of Congo in 1970 when there were intensive attempts to eliminate smallpox.

It has been reported in humans in other central and western African countries since then.

Human infection has been reported in the United States in 2003 (47 cases); the United Kingdom (three cases) and Israel (one case) in 2018; and in Singapore in 2019.

The monkeypox virus is about 96% genetically identical to the smallpox virus. However, monkeypox infection is clinically less severe than smallpox.

Monkeypox infection occurs in many animals, i.e. rope and tree squirrels, rats, mice and primates in central and west Africa.

The Central African infection is more severe than the West African one with a higher mortality or death rate.

Spread from one human to another has been well-documented with the Central African virus, and less so with the West African virus.

Infection occurs from direct contact with the blood, body fluids, or skin or mucosal lesions of infected animals, with rodents the most likely reservoir of the virus.

The consumption of inadequately cooked meat of infected animals is a possible risk factor.

The virus enters the human body through broken skin, the respiratory tract or mucous membranes of the eyes, nose or mouth.

Transmission between humans can occur with close contact with the infected respiratory secretions or skin lesions of an infected person, and/or objects recently contaminated by the fluids, lesions, clothing or bedding of an infected person.

Transmission occurs mainly from respiratory droplets, requiring close face-to-face contact, as the droplets cannot travel more than a few feet in the air.

This means that those at greater risk of infection are the infected person’s household members and healthcare staff.

Clinical features

The interval between the infection and onset of symptoms, known as the incubation period, is usually six to 16 days, but can range from five to 21 days.

The initial phase, which can last up to five days, is characterised by fever, severe headache, back pain, muscle ache, swelling of lymph nodes (lymphadenopathy) and abnormal weakness.

The main difference between monkeypox and smallpox is the presence of lymphadenopathy in the former and absence in the latter.

Skin rashes appear within one to three days after the onset of fever. It frequently starts in the face and then spreads to the rest of the body with the face, palms of the hands and soles of the feet most affected.

The rash changes from flat lesions (maculopapules) to fluid-filled blisters (vesicles), pus-filled blisters (pustules) and crusts in about 10 days.

The crusts may take about three weeks to disappear.

Monkeypox infection is usually self-limiting with the clinical features lasting one to two weeks.

The death rates have been less than 10% in documented cases, with severe infections more common in children.

Monkeypox has to be distinguished from other illnesses with rashes, which include smallpox (although this has been eradicated), chickenpox, measles, bacterial skin infections, scabies, syphilis and drug allergies.

The diagnosis of monkeypox can only be confirmed by specialised laboratories. The samples tested are taken from the patient’s skin lesions.

Management

There is no specific treatment or vaccine for monkeypox infection.

The smallpox vaccine has been proven to be 85% effective in preventing monkeypox infection in the past, but it is not commercially available now.

However, there is a stockpile of smallpox vaccine held by the World Health Organization, France, Germany, Japan, New Zealand and the US for any re-emergence of smallpox.

The only way to reduce possible human infection is to reduce exposure to the virus, with surveillance and rapid identification of new cases vital in containing an outbreak.

The reduction of the risk of animal-to-human transmission involves the avoidance of any contact with rodents and primates; limiting direct exposure to blood and meat of animals; and thorough cooking prior to eating.

The usage of gloves and protective clothing when handling sick animals or their tissues, and during the slaughtering of animals, is essential.

The reduction of the risk of human-to-human transmission involves the avoidance of close physical contact with those infected and contaminated objects.

The usage of gloves and personal protective equipment (PPE) is necessary when taking care of the sick.

Regular handwashing with soap and water, or the use of alcohol-based hand sanitisers, should be carried out after caring for, or visiting, the sick.

Isolation or quarantine of patients in hospital or at home has been recommended.

Healthcare staff caring for patients with suspected or confirmed monkeypox infection, or who are handling their specimens, have to adhere strictly to standard infection control procedures.

Those treating or exposed to patients with monkeypox infection or their bodily secretions or lesions have to be considered for smallpox vaccination, which reduces the severity of monkeypox infection.

The samples taken from people and/or animals suspected of monkeypox infection have to be handled by trained staff who adhere strictly to the standard operating procedures of the specialised laboratories, which includes safe packaging and guidelines for infectious materials.

The restriction or banning of the movement of small African monkeys and mammals may slow the spread of the virus outside Africa.

The quarantine of animals with potential infection by the monkeypox virus and that of animals that have come into contact with such animals could also be helpful.

Dr Milton Lum is a past president of the Federation of Private Medical Practitioners Associations and the Malaysian Medical Association. The views expressed do not represent that of organisations that the writer is associated with. The information provided is for educational and communication purposes only and it should not be construed as personal medical advice. Information published in this article is not intended to replace, supplant or augment a consultation with a health professional regarding the reader’s own medical care. The Star disclaims all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.