Human Monkeypox

Monkeypox is an emerging disease. It was first discovered in 1958 in a captive monkeys population, from which it received its name. However, monkeys are not its main reservoir. The largest natural reservoir population is the rodents. The full lifecycle and the extent of the reservoir population are still unknown.

Monkeypox is a zoonosis.

The virus

It is a double-stranded DNA virus. It belongs to the family poxviridae, genus Orthopoxvirus.

It has two genetic clades – the west African variant and the central African variant. The west African clade usually causes milder disease with limited human-to-human transmission compared to the central African clades.

Image source: University of Wisconsin-La Crosse, Microbiology program

Distribution

The virus is endemic in central and west Africa. Most cases have been reported from the DRC Congo and Nigeria. The first human Monkeypox case was found in 1970. However, the numbeypox cases has increased significantly in recent decades.

7 cases have been diagnosed in the UK, all related to travel/imported cases. (UKSHA, WHO)

Monkeypox endemic countries are: Cameroon, the Central African Republic, the Democratic Republic of the Congo, Gabon, Ghana (identified in animals only), Cote d’Ivoire, Liberia, Nigeria, the Republic of the Congo, and Sierra Leone. Benin and South Sudan have documented importations in the past. Countries currently reporting cases of the West African clade are Cameroon and Nigeria.

Image credit: WHO

Monkeypox outbreak 2022

In 2022 a multi-country outbreak happened affecting gay, bisexual and men having sex with men (MSM) population. The update on the outbreak could be seen on WHO website. As per the updated report 780 people in 27 countries are affected (28/6/22).

Multi-country monkeypox outbreak: situation update (who.int)


Latest guideline on Monkeypox from UKHSA can be accessed here - Monkeypox: background information - GOV.UK (www.gov.uk)

Clinical presentation

Incubation period of Monkeypox

  • The incubation period of Monkeypox is 7−14 days (range – 5−21 days).

Clinical features

  • The incubation period is followed by prodromal syndromes (also called invasion period) -with flu-like illness (fever, malaise, headache, sore throat, cough), asthenia (lack of enery) and lymphadenopathy. Lymphadenopathy, which could be generalised or localised (axilla/neck), is a feature that differentiates monkeypox from smallpox.


  • After the prodrome, the rash appears (usually after 1-5 days of fever), appearing in any part of the body but most common on the face. It can also affect the mucous membrane of the mouth, cornea and conjunctiva. The rash progresses through four stages—macular, papular, vesicular, to pustular, eventually forming scabs before resolving (taking approximately 2 weeks). Pitted scars may remain after the resolution of the rash.

Different stages of rash. Source: https://www.gov.uk/guidance/monkeypox

How long is Monkeypox infectious?

  • The patient remains infectious until the scabs are fallen off.

What is the mortality of Monkeypox?

  • Mortality is approximately 10%. Severe disease is more common, and mortality is higher in children. (WHO)

Complications of Monkeypox

  • Secondary infections,

  • Bronchopneumonia,

  • Sepsis,

  • Encephalitis, and

  • Corneal infection/keratitis leading to loss of vision.

Transmission of virus

  • Animal to human transmission occurs via – bite, scratch, direct contact with infected material or bushmeat consumption.

  • Human to human transmission – contact with body fluid or infected lesion, aerosol transmission (coughing, sneezing).

  • Indirect transmission – via material contaminated with body fluid/lesion.

The virus enters the body through broken skin or mucous membrane.

Investigation

  • Monkeypox should be clinically differentiated from other rash illnesses like chickenpox. It is difficult, but lymphadenopathy may help to differentiate the disease.

  • It is an ACDP category 3 pathogen. The laboratory must be notified before sending specimens.

  • Suspected cases should be discussed with the Imported Fever Service for investigation in RIPL, Porton Down – vesicle fluid/crusts/swab for RT-PCR.

Infection control and Public Health

  • Monkeypox is an ACDP category 3 pathogen.

  • Immediate notification to Public Health England and Infection prevention control team.

  • Isolation, negative pressure room preferred. (CDC).

  • Standard, contact and respiratory precaution.

  • PPE including FFP3 mask.

PHE has a guideline for environmental cleaning - It is available on this page


Treatment

  • There is no specific treatment. Management is mainly supportive.

  • In most cases, the disease is mild, and the patient recovers within 2-4 weeks.


Vaccine:

Smallpox vaccine – Past data from Africa suggests that the smallpox vaccine is at least 85% effective in preventing monkeypox (CDC) – CDC considers it for outbreak type situations.


Other treatments with limited data from animal studies or no significant data – Cidofovir, Brincidofovir, Tecovirimat (ST-246), Vaccinia Immune Globulin. (CDC).