Mpox (also known as monkeypox)

Click here to view the thematic webpage of Mpox

Causative agent

Mpox (also known as monkeypox) is a zoonosis caused by monkeypox virus. First discovered in 1958 in monkeys kept for research, hence the virus was named ‘monkeypox virus’. On 28 November 2022, WHO recommended “mpox” as a synonym of the disease in English.

Human infection of monkeypox was given its name since 1970 when the first case was reported in the Democratic Republic of Congo (then known as Zaire). From that time, most of the reported outbreaks have occurred in Central and West Africa, and some outbreaks outside Africa were found to be related to the imported animals or travelers from Africa. Since May 2022, there has been a multi-country outbreak reported globally, leading the World Health Organizaton (WHO) to declare mpox as a Public Health Emergency of International Concern (PHEIC) during July 2022 to May 2023. In response to another round of outbreak in Africa, the WHO again declared mpox as PHEIC on 14 August 2024.

Clinical features

For some patients, the first few days after infection with mpox are characterised by fever, intense headache, sore throat, myalgia and lymphadenopathy. The rashes appear about 1 to 3 days after onset of fever. For others, the first symptom could be a rash. Lesions can start on the face and spread over the body, extending to the hands and feet. It can also start on other parts of the body where contact was made, such as the genitals, anus or mouth. The lesions progress from maculopapules to vesicles, pustules and followed by crusts and fall off.

Some patients may present with painful proctitis or painful and difficult urination. Some people can also be infected without developing any symptoms.

Mpox is usually a self-limited disease with symptoms lasting from 2 to 4 weeks but may last longer in someone with a weakened immune system. Children, pregnant women and people with weakened immune systems also have a higher risk of serious illness and death. The case fatality in previous 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 mainly through close contact with infected individuals, such as skin-to-skin, mouth-to-mouth, mouth-to-skin, and sexual contact (transmitted via saliva or body fluids. The virus may also be passed to the baby during pregnancy or birth, which may cause serious complications for the baby or the mother. However, the likelihood of transmission through respiratory droplets is relatively low.

Incubation period

The incubation period is usually from 6 to 13 days, with a range from 1 to 21 days.

Management

In principle, treatment of mpox includes the control of symptoms, management of complications and the prevention of long-term sequelae. Secondary bacterial infections should be treated as indicated. Some antiviral agents are used for the treatment of mpox in severe cases under emergency use authorization and relevant effectiveness of antiviral treatments are being evaluated in clinical trials.

Prevention

Mpox vaccines provide protection against infection and severe disease. The Government has procured a third generation vaccine called "JYNNEOS" by making reference to the earlier recommendations of the Scientific Committee on Vaccine Preventable Diseases and the Scientific Committee on Emerging and Zoonotic Diseases as pre-exposure and post-exposure vaccination. The vaccine has arrived in Hong Kong in September 2022 to be used in the Mpox Vaccination Programme.

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

• Avoid close, skin-to-skin contact with sick people or people with a rash that looks like mpox;
• Avoid contact with objects and materials that a person with mpox has used, such as eating utensils or cups, bedding, towels, or clothing;
• Avoid contact with sick or dead animals;
• Implement appropriate infection control precautions when taking care of ill people or handling animals, such as wearing protective clothing and equipment including gloves and surgical masks;
• Maintain hand hygiene. Clean hands with liquid soap and water when they are visibly soiled or likely contaminated with blood and body fluid. When hands are not visibly soiled, they could be cleaned with 70-80% alcohol-based handrub;
• Thoroughly cook all animal products before eating; and
• Seek medical advice promptly for any suspicious symptoms.

Other languages