Mpox Outbreak 2023

Overview

The 2022-2023 global mpox outbreak marked the first time high incidences of mpox (previously known as monkeypox) were documented outside of Central and West Africa. This unprecedented epidemic is the largest mpox outbreak recorded in both magnitude and geographical spread. 

The first case was identified in London in a patient with a travel history to Nigeria (a country endemic to mpox). Following the first report, four cases were confirmed on the 16th of May, 2022, however, these cases had no known connections with the previously confirmed cases and no links to travel within any endemic regions.¹ After multiple cases were reported from other non-endemic countries, this led to the declaration of the outbreak as a public health emergency by the World Health Organisation (WHO).² 

Overall, this epidemic was considered atypical due to the sustained community transmission within non-endemic countries. Within this article, we will explore what mpox is and how the recent outbreak spread globally. 

What is mpox?

Mpox is a zoonotic disease caused by the monkeypox virus. This virus belongs to the genus Orthopoxvirus. It is closely related to the smallpox and cowpox viruses, which belong to the same genus.

The former name of the disease “monkeypox” was derived following its discovery and isolation from monkeys in 1958 by researchers in Denmark. Nevertheless, other wild animals have also been shown to be susceptible to the virus. This includes rodents such as rats, mice, and squirrels.³

Two distinct clades of mpox exist, the Central African Clade I and the West African Clade II. Clade is a term used to describe a virus subgroup with genetic variations. Clade II is said to be less pathogenic and more commonly responsible for mpox cases occurring outside of Africa. The 2022-2023 outbreak was caused by Clade IIb (a subtype of the West African Clade II).⁴ 

How do you get mpox?

Mpox is transmitted from person to person via direct contact. This includes:

• close physical contact with mpox rash or scabs (i.e., during sexual contact, kissing, holding hands, or hugging)
• coughs or sneezes

Albeit less likely, mpox can also be passed on by touching contaminated objects. This may include contact with the clothing, bedding, or towels of someone infected with mpox (that has not been disinfected).⁵ 

Animal-to-human transmission of mpox can also occur in regions of West and Central Africa. Infected rodents (e.g., rats, mice, squirrels) can spread mpox to humans through:

• bites or scratches
• contact with their fur, skin, blood, body fluids, blisters, or scabs
• eating their meat when it has not been fully cooked 

This can happen during the hunting and processing of infected wild animals.⁶ 

What are the symptoms of mpox?

It takes approximately 5-21 days (within 3 weeks) for symptoms of mpox to appear. The first signs of mpox include:

• a high temperature (fever, 38°C or above)
• headache
• muscle aches
• backache
• swollen glands
• shivering (chills)
• fatigue/exhaustion
• joint pain
• respiratory symptoms (e.g., sore throat, blocked nose, or cough)

Following the appearance of the symptoms listed (above), a rash usually appears within 1-5 days. The rash begins on the face and then spreads to other areas of the body (e.g., mouth, genitals, and anus). Individuals with mpox may experience anal pain or bleeding from the bottom as a result of the rash.

The rash can be mistaken as chickenpox, due to its similar appearance. Initially, the rash looks like pimples or raised spots and may be painful or itchy. These spots become small, fluid-filled blisters, eventually forming scabs and falling off. 

Although symptoms are normally mild and clear up after a few weeks, whilst you are symptomatic you can still transmit mpox to other people. Isolation and wearing face masks are recommended.⁵

Causes and origins of the outbreak

In May 2022, an atypical outbreak of mpox was declared following an increase in cases throughout Europe. The first case was reported in London, on 6 May 2022, in a patient who had recently travelled to Nigeria. Following the reported cases in the UK, outbreaks were identified globally. This was considered unusual as these countries are not endemic to the disease. Subsequently, on 23 July 2022, WHO announced this outbreak was a Public Health Emergency of International Concern (PHEIC).² 

Another reason the outbreak was considered unusual was that previous mpox cases diagnosed in the UK documented no community transmissions. Before 2022, prior cases in the UK had either been spread following travel to countries endemic to the virus or through contact with epidemiological links to those imported cases. The reason for this significant difference was due to a change in the route of transmission. 

Previously, the main transmission route was believed to be between animals and humans (zoonotic transmission). However, the 2022-2023 outbreak provided evidence to suggest that this particular epidemic was mostly spread due to close sexual contact. This posed a fundamental change in the epidemiology of mpox and has significant implications for future surveillance and responses to potential rises in mpox cases.⁷ 

In the UK, the UK Health Security Agency (UKHSA) implemented extensive public health measures to prevent the spread of mpox. This involved isolation of those infected, contact tracing, and awareness training.⁸ The UKHSA also recommended pre-exposure vaccination for high-risk groups. Vaccination plays an essential role in the prevention and reduction of mpox incidences. 

This is demonstrated in a 2023 review of cases in England, where a single dose of the MVA-BN (Modified Vaccinia Ankara–Bavaria Nordic smallpox vaccine) was shown to provide 78% protection against mpox for 14 days.⁹ 

Treatment and management of mpox

Most people infected with mpox have mild symptoms and recover within a few weeks without treatment. 

In the case that your symptoms are more severe, then you may require treatment in hospital. The following people have a higher risk of having severe symptoms:

• older people
• young children
• people who are immunocompromised (this may be due to a condition or if you are taking immunosuppressants)

Regardless of the severity of your symptoms, all individuals diagnosed with mpox should isolate to prevent transmission to others. This is because mpox can be passed on to others via close contact.⁵ 

GOV.UK provides additional advice for those with mpox isolating at home.

Currently, there aren’t any antiviral treatments that specifically target mpox. If you have severe symptoms, you may be prescribed existing drugs for smallpox, as these have been shown to provide protection.¹⁰ These include:

• Cidofovir
• Tecovirimat

Mpox vaccination

Mpox is caused by a monkeypox virus which is closely related to smallpox. Hence, the smallpox vaccine (MVA) can provide effective protection against mpox as well. 

Who can get the mpox vaccine?

Presently, the NHS offers the mpox vaccine for those who are at higher risk of exposure. 

People most likely to be exposed to mpox include:

• healthcare workers caring for patients with mpox 
• Those assigned male at birth (AMAB) who are gay, bisexual or have sex with other people AMAB, and who have multiple partners, participate in group sex or attend sex-on-premises venues (staff at these venues are also eligible)

People in close contact with someone with mpox should be given a single dose of the vaccine within 4 days of contact. However, if needed, it can be given up to 14 days later. Healthcare workers will be offered 2 doses of the vaccine. You will be contacted by your local NHS services when you can receive the second dose. The second dose will be administered around 2 to 3 months after the first dose.⁵ 

The NHS provides more information on how to find a vaccination site.

FAQs

How many cases of mpox were there in the UK in 2023?

In 2023, there were 143 mpox cases reported in the UK. However, the total number of confirmed cases from 2022 and 2023 is 3,875 (this figure is based on data extracted on the 3rd of January 2024, and includes cases identified from 6 May 2022 to 31 December 2023).¹¹

Who is at risk for mpox?

Although the majority of cases from the recent outbreak were reported among gay people AMAB, the risk of mpox is not exclusive to this community. Anyone who has close contact with a person who is infected with mpox will be at risk, regardless of their sexual orientation. 

The WHO states people with multiple or new sexual partners are most at risk, as well as, people who have a higher exposure to mpox such as household members or healthcare workers.¹² 

What is the death rate of mpox?

Clade I has a fatality rate of approximately 10%. Whereas, Clade II infections are rarely fatal, with a fatality rate of less than 1%.^13,14 

Is mpox an STD?

Although mpox is more common among gay people AMAB and is spread via intimate skin contact which may occur during sexual activities, it is not classified as an STD. This is because mpox is not transmitted via seminal or vaginal fluid. It is transmitted either person-to-person or animal-to-person.¹⁵

Summary

Mpox is a viral disease that causes smallpox-like symptoms such as rash, fever, and swollen glands. Although mpox is typically a rare infection endemic to West and Central Africa, there has recently been a rise in cases globally. The largest outbreak (in size and geographical spread) was reported during 2022-2023. 

The virus was predominantly spread among gay people AMAB and was initially identified following a report in England, in May 2022. Research and appropriate preventative measures allowed for the reduction in incidences and have helped us understand the evolution of its epidemiology. Initially, the outbreak was considered unusual, as community transmissions within non-endemic countries had not been previously documented. 

The newfound understanding of mpox’s transmission through close, intimate contact will help control and prevent future outbreaks.