See the mpox collection page for further resources including guidance for health professionals.

Origin and spread of mpoxEpidemiology

Mpox is an infectious disease that is caused by theinfection with a virus called MPXV virus.

. Mpox was first discovered in 1958 when outbreaks of a pox-like disease occurred in monkeys kept for research.

The first human case was recorded in 1970 in the Democratic Republic of the Congo (DRC).), Sinceand since then the infection has been reported in a number of African countriescountries. and,Prior moreto recently,2022 hasmost spreadcases towere multiplereported countriesfrom around the world.DRC Thisand includesNigeria.

In cases2003, mpox was recorded in the UK.

ThereUS arewhen 2an majoroutbreak typesoccurred following the importation of MPXV.rodents Thesefrom areAfrica. calledCases cladeswere reported in both humans and arepet knownprairie asdogs. cladeAll Ithe andhuman cladeinfections II.followed Cladecontact Iwith wasan previouslyinfected knownpet asexposed Centralto Africanan orimported Congoanimal basinand clade,all afterpatients therecovered.

There placesare it2 wasmajor originallygenetic found.groups Clade(clades) IIof wasMPXV, previouslyclade I (formerly known as WestCentral African clade.

Sub-typesor ofCongo eachbasin clade) and clade haveII been(formerly identified.known as West African clade). Clade I is split into clade Ia and clade Ib. Clade II is split into clade IIaIIb and clade IIb.IIa, Thesewith cansubgroup beclusters brokencalled downlineages. furtherThe intomajority groupings calledof lineages.the Thiscases isseen importantin asthe weoutbreak canin track2022 differentwere outbreaksfrom clade IIb, lineage B.1.

Since May 2022, cases of human mpox aroundhave thebeen worldreported byin lookingmultiple atcountries that have not previously had MPXV in animal or human populations, including the exactUK. typeThe majority of thethese mpoxcases virusesare involved.from clade IIb, lineage B.1.

Historically,Since January 2023, clade II mpox wasis knownno tolonger haveconsidered beena occasionallyhigh passedconsequence oninfectious fromdisease infected(HCID) animalswithin tothe humans,UK. withClade humansI sometimesmpox passingremains itan onHCID. toThere otheris peoplefurther thatinformation theyon hadthe closeHCID contactstatus with.of Sincempox Mayavailable. 2022Further however,information caseson the epidemiology of humanmpox is available in the mpox haveepidemiological overview.

Clade I MPXV has previously been reportedintermittently intransmitted multiplefrom countriesanimals thatto havehumans, notwith previouslysmall hadmammals and primates acting as hosts. Clade I MPXV incan animalalso orspread humanvia populations.human-to-human Thistransmission hasand includedhad casespreviously been associated with close contact. However, in theMarch UK.2023, Thisinfections ongoinglinked outbreakto issexual mostlycontact causedand byinternational cladetravel IIb,were lineagereported B.1in MPXVthe DRC, andfor isthe spreadfirst mostlytime.

Mpox by2024

Historically, sexualclade contact.I mpox was known to circulate in 5 Central African Region countries:

Since

• Cameroon
• Central AugustAfrican Republic (CAR)
• the Democratic Republic of the Congo (DRC)
• Gabon
• the Republic of the Congo

In 2024, clade I MPXVmpox hascases alsowere been reported from multiple countries outsidebeyond ofthese the5 Central African regionRegion thatcountries. hadThis notis previouslylikely reportedto it,be because of multiple factors including caseswaning inpopulation immunity from the UK.discontinued Thissmallpox isvaccine mostlyand causedchanging byenvironmental cladeand Ibsocial MPXV,factors, andbut isthe spreadfull mostlyaetiology throughremains closeunclear. physicalSee contactthe (includingcountries bothaffected sexualby andclade non-sexualI contact).mpox.

FurtherClade informationI onmpox thewas epidemiologydetected of mpox in the UK isfor availablethe first time in the2024; mpoxsee epidemiologicalthe overview.

Informationinformation on countriesconfirmed currentlycases affectedof byclade Ib mpox isfor availablefurther and updated regularly by UKHSA.information.

Transmission

Mpox does not spread easily between people unless there is close contact.

Spread between people may occur through:

• direct contact with rash, skin lesions or scabs (including during sexual contact, kissing, cuddling or other skin-to-skin contact)
• contact with bodily fluids such as saliva, nasalsnot mucus or semen/vaginal fluidsmucous
• contact with clothing,clothing linenor linens (such as bedding or towels) or other objects and surfaces used by someone with mpox

It is possible that clade I mpox may spread between people through close and prolonged face-to-face contact such as talking, breathing, coughing, or sneezing close to one another. However, there is currently limited evidence so this will be updated as new information is available.

Spread of mpox may also occur when a person comes into close contact with an infected animal (rodents are believed to be the primary animal sourcereservoir for transmission to humans), or materials contaminated with the virus. Mpox has not been detected in animals in the UK.

Clinical features

The incubation period is the timeduration/time between contact with the person with mpox and whenthe time that the first symptoms appear. The incubation period for mpox is between 5 and 21 days.

MostMpox peopleinfection whois catchusually mpoxa willself-limiting recoverillness withinand severalmost weekspeople withoutrecover anywithin treatment.several weeks. However, severe illness can occur in some individuals. HCID mpox is known to cause more severe disease than non-HCID mpox clades with case fatality rates of 10% reported in non-vaccinated individuals previously.

The illness begins with:

• fever
• headache
• muscle aches
• backache
• swollen lymph nodes
• chills
• exhaustion
• joint pain

However, not all people who have mpox experience all of these symptoms.

Within 1 to 5 days after the appearance of fever, a rash develops, often beginning on the face then spreading to other parts of the body including the soles of the feet and palms of the hands. TheLesions rash can also affect the mouth, genitals and anus.

The rash ischanges made up of a variable number of lesions. These lesions change and gogoes through different stages,stages shownbefore in the images below. The lesions finally formforming scabs which eventually fall off.

Some individuals may not have a widespread rash, and in some cases only genital lesions are present. These may be blisters/vesicles, scabs or ulcers.

SomeoneAn whoindividual has mpox is contagious until all the scabs have fallen off and there is intact skin underneath. The scabs may also contain infectious virus material.

Images of individual mpox lesions

Notes

TheAreas lesions may have areas of rednesserythema orand/or darker patches of skin aroundhyperpigmentation them.are Lesionsoften onseen blackaround ordiscrete brown skin may be harder to see.lesions.

Lesions can vary in size and may be larger than those shown in these images.shown.

Lesions of different appearances and stages may be seen at the same point in time. The

Detached scabs that fall off may be considerably smaller than the original lesion.

Diagnosis

DiagnosisClinical diagnosis of mpox can be difficult, and it is often confused with other infections such as chickenpox. A confirmeddefinite diagnosis of mpox requires assessment by a health professional and specific testing in a specialist laboratory.

In See the informationUK, ontesting whenis toprovided suspectby mpox,many includingNHS actionslaboratories, forand suspectedis cases.

Inalso available at the UK,Rare testingand isimported availablepathogens laboratory (RIPL) at the UK Health Security Agency (UKHSA) RarePorton andDown.

Patients Importedwith Pathogensa Laboratorytravel (or exposure history indicating possible HCID mpox should be discussed with the RIPL), nationalclinical laboratoriesteam inas soon as possible via the devolved24/7 administrationsImported andFever someService NHShelpline and(0844 private778 laboratories.8990).

UnlessAll cladesamples testingfrom isall availableindividuals locally,testing all positive samplesfor shouldmpox must be forwardedsent to RIPL for clade testingdifferentiating astests. part of ongoing surveillance. Samples from suspected and confirmed cases of mpox should be shipped as Category B diagnostic samples. See guidance on diagnostic testing for information on how to submit samples for testing.

Treatment

Treatment for mpox is mainly supportive,supportive. whichNon-HCID meansmpox it is aimedusually atmild treatingand themost symptomsof whilethose yourinfected bodywill fightsrecover thewithin infection.a few weeks without treatment.

Antiviral drugs such as cidofovir and tecovirimat can be used to treat mpox patients with severe disease or those who are at high risk of severe disease.

Smallpox vaccine can be used to reduce the likelihood of infection in high risk groups and to support the control of outbreaks of mpox. WhilePeople it may not prevent infection entirely, people vaccinated against smallpox (including in childhood)childhood may experience a milder disease. Vaccines have been used to protect high risk individuals during outbreaks.

Infection prevention and control

AppropriatePrevention precautionsof aretransmission essentialby whenrespiratory managingand suspectedcontact androutes confirmedis cases,required. thereforeAppropriate preventionprecautions ofare transmissionessential byfor contactsuspected and respiratoryconfirmed routescases. is required. Scabs are also infectious and care must be taken to avoid infection through handling bedding and clothing. Information on infection prevention and control measures withinare healthcare settings is available in the NationalNHS Infectionguidance Preventionon infection prevention and Controlcontrol Manualmeasures for Englandclinically suspected and confirmed cases of mpox in healthcare settings.

Mpox virus is classified as an ACDP Hazard Group 3 pathogen and all laboratory work with live virus must be conducted at full Containment Levellevel 3 (CL3), in accordance with the Control of Substances Hazardous to Health Regulations 2002 (as amended). See the guidance on diagnostic testing for further information on handling specific sample types.

Laboratories must ensure that appropriate controls commensurate to CL3 are in place to minimise risk to laboratory workers so that they can safely perform laboratory tests that are essential to clinical care.

Further information

See WHO factsheet.

Additional mpox resources are also available on GOV.UK, including information on:

• on when to suspect mpox
• contact, contact tracing for clade I
• and clade II mpox and vaccination

.