What you need to know about mpox

Mpox, which was previously known as monkeypox, first became a concern in 2022 during a global outbreak. This outbreak involved a strain of the virus called clade IIb, which is normally found in areas of west and central Africa. The virus spread among specific at-risk groups causing clusters of infections worldwide. Clade IIb continues to circulate in many countries globally as a result of this 2022 outbreak.

The current emergency involves a different strain, called clade Ib. The Democratic Republic of Congo (DRC) has seen the largest outbreak of this new strain, and it has begun spreading to other countries like Burundi, Rwanda, Uganda and Kenya.

As of 5 September, Burundi is the worst impacted country outside of DRC where we are seeing sustained local community transmission, reporting 328 confirmed cases. Uganda has recently updated the total to ten confirmed cases, which indicates that there is potentially local transmission; given these statistics it can be inferred that Rwanda may be underreporting case numbers. As of 2 September, Sweden and Thailand are the only countries outside Africa that have reported cases of clade Ib, both cases had recent travel history to affected areas.

Data from the DRC shows that the virulence of mpox clade Ib is greater than the mpox clade IIb. This new strain is more contagious and has a higher case fatality rate. Unfortunately, in the DRC, children seem to be affected more than adults. Data on how infectious and how virulent mpox clade Ib is outside of the DRC is still being studied. It’s not clear yet whether the higher fatality is due to other health problems in patients, like being malnourished, or if this strain of the virus is just more deadly.

What is mpox?

Mpox is caused by a virus which is endemic (naturally occurs) in parts of central Africa. It is a pox virus, closely related to smallpox and cowpox. Because smallpox and mpox are closely related, the smallpox vaccine has a good efficacy against mpox infection. Even though smallpox no longer exists in the wild, many countries have kept a stock of smallpox vaccines in case of an accidental or deliberate leak of smallpox virus from a laboratory or bioweapon programme. This is now helpful because the smallpox vaccine can be used to reduce the spread of mpox.

How is mpox spread, and what are the symptoms?

Both types of mpox are spread in similar ways - through close contact with an infected person, especially if they have a characteristic rash, or by touching contaminated items that have been in contact with an infected person. Mpox mainly spreads through close family contacts, like from a parent to child and vice versa, or through sexual contact. The incubation period from infection to symptoms is 4 - 11 days.

The first symptoms of mpox infection can feel like the flu, with fever, muscle aches and sore throat. After that, a painful rash develops with fluid-filled blisters. Some people might only get one or two lesions, while others will develop a widespread rash. These symptoms usually last for about 10 days.

The risk of developing complications from an mpox infection is higher in very young and elderly patients, as well as in those with weakened immune systems, such as people with HIV or those on immunosuppressive medication. The global case fatality rate for mpox IIb was around 0.16%, but the case fatality rate for mpox Ib clade seems much higher, with some estimates reaching up to 12%.

Treatment and prevention of mpox

There is no specific cure for mpox infection. Most cases of mpox don’t need specific treatment, just pain-relief. The smallpox vaccine can help prevent mpox infection. It is sold under the names Jynneos, Immune or Imvanex and is available in some countries for people in at-risk groups. Vaccination can also be given after a person has been in contact with someone infected with mpox. In this case vaccination should be given within four days of the contact. It is not available as a travel vaccine. The World Health Organization recommends pre-exposure vaccination for individuals believed to be at high risk of mpox infection. This would include:

• Healthcare staff or other care workers who may be required to look after patients with mpox

• Sex workers, as well as clients of sex workers

• People who have multiple sexual partners, including men who have sex with men

• People in the same household, or who have close contact with, someone with mpox

The vaccination is given as two doses, 28 days apart. The maximum protection against mpox is achieved two weeks after the second dose. Mpox vaccination is not widely available in all countries, and arrangements to distribute the vaccine differ significantly from country to country. Not all health authorities are using the same criteria to determine eligibility for the vaccine.

To lower the risk of mpox infection, avoid contact with small mammals and monkeys/apes in West and Central Africa. It’s also important to avoid close and skin-to-skin contact with anyone who is sick or has a blistering rash. Good hand hygiene is also recommended, especially when travelling to areas at risk.

Assessment of current situation and travel advisory

Due to the high amount of global travel, it’s very likely that mpox clade Ib is already spreading outside of Africa, and new cases will probably be reported in the coming days and weeks.

It seems likely that the virus will mainly affect specific at-risk groups, many of whom were vaccinated during the 2022 mpox outbreak. The declaration of a public health emergency of international concern will allow for better monitoring and surveillance. It’s important to stay informed about local outbreak trends, especially when traveling.

Currently there are no specific travel restrictions in place. However in parts of Africa, there is likely to be increased surveillance both in-country and at points of entry, which is likely to cause delays to travel.

With increased surveillance of the disease, increased case numbers are expected to be reported of both clades of mpox. However, it’s important to note that this may be due to increased testing and awareness, rather than increase prevalence. It should also be noted that due to limited diagnostic capability and sequencing in many affected countries the clade of mpox is not always confirmed so mpox case numbers are reported together.

Mpox is likely to continue to spread with the sustained momentum. In the coming weeks it is expected that more countries outside of Africa will report isolated incidents of clade I mpox, however isolated incidents are typically not concerning.

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