Monkeypox

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Causative agent

Monkeypox is a zoonosis caused by monkeypox virus. The virus was first discovered in 1958 in monkeys kept for research, and hence the disease was named ‘monkeypox’.

Since first reported in humans in 1970 in the Democratic Republic of Congo (then known as Zaire), most of the reported monkeypox outbreaks have occurred in Central and West Africa.

Clinical features

The symptoms are similar to those of smallpox, but in milder forms. The first few days after infection with monkeypox are characterised by fever, intense headache, myalgia and lymphadenopathy. Severe swollen lymph nodes before the appearance of rash could be a distinctive feature of monkeypox. Lesions in mouth and body appear about 1 to 3 days after onset of fever. The lesions progress from maculopapules to vesicles, pustules and followed by crusts within a period of 10 days to two weeks and the lesions typically progress simultaneously at all parts of the body.

Monkeypox is usually a self-limited disease with symptoms lasting from 14 to 21 days. The case fatality in previous monkeypox outbreaks has been between 1% and 10%.

Mode of transmission

Infection could occur when a person comes into contact with the virus from infected animals, infected humans or contaminated materials. Humans could get infected from various wild animals, such as some species of primates, rodents and squirrels, etc., through bite or scratch, or direct contact with their body fluids. Human-to-human transmission is also possible through respiratory droplets during prolonged face-to-face contact or direct contact with body fluids.

Incubation period

The incubation period is usually from 6 to 13 days, with a range from 5 to 21 days.

Management

There is currently no registered specific vaccine or antiviral pharmaceutical product for monkeypox available in Hong Kong. It has been shown that smallpox vaccine may also be effective in preventing monkeypox, and a new vaccine called "Jynneos" has been licensed by the U.S. Food and Drug Administration (FDA) for the protection of monkeypox in 2019. A new antiviral drug was approved for the treatment of monkeypox in Europe recently.

Prevention

To reduce the risk of infection, members of the public travelling to places affected by monkeypox virus should:

• Avoid close physical contact with sick persons or animals;
• Wear protective clothing and equipment including gloves and surgical masks when taking care of ill people or handling animals, and carry out regular hand washing after these procedures;
• Thoroughly cook all animal products before eating; and
• Seek medical advice promptly for any suspicious symptoms.

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