As of 27th June 2022, the WHO declared MPox an “Evolving global health threat“. Here is what we know so far…..
What is it?
Mpox is a double-stranded DNA virus and a member of the poxviridae family. They infect a range of creatures, including reptiles, birds, insects, and mammals. Interestingly the main reservoir is rodents, (specifically the African giant pouched rat and squirrels).
Still, sporadic outbreaks occur in primates, e.g. monkeys, who seem to have taken unfortunate credit and monopolised the name! Eleven poxvirus species have been shown to cause human infections – the other well-known member of the family is Variola (smallpox). Smallpox led to over 300 million fatalities worldwide.
The impact of this is a reminder to take these poxviruses seriously. International immunisation programmes against smallpox ended over 40 years ago. Many of the population do not have immunity against it and other orthopoxviruses. The worry is that with more infections and reduced immunity, a zoonotic virus, like Mpox, might gain the ability to transmit more efficiently between humans and cause more significant outbreaks.
Why has it made it to the headlines recently?
Mpox is not a new virus. It is endemic to some regions of Central and Western Africa (Cameroon, Central African Republic, Cote d’Ivoire, Democratic Republic of Congo, Gabon, Liberia, Nigeria, Republic of Congo, Sierra Leone, and South Sudan). Most cases tend to arise sporadically or are related to local outbreaks. Cases outside endemic areas tend to be linked with international travel or host contact.
There are two distinct types, or “clades” (clade: a group of organisms believed to comprise all the evolutionary descendants of a common ancestor). These are currently known as West African and Central African clades. The West African clade tends to result in a more self-limiting condition, with fatality rates estimated at less than 1%. The Central African clade has been associated with case fatality rates of up to 10%. As of writing, the West African clade has been isolated in outbreaks this year.
This year, cases have been reported in non-endemic countries: the UK, Australia, Belgium, Canada, France, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, and the USA. As of July 2022, there are 1735 confirmed cases of Monkeypox in the UK*. Before 2022, only a handful of cases were recorded in non-endemic countries.
How do you contract Mpox?
Animal-to-human transmission of Mpox is thought to occur through the handling of infected meat or via bites and scratches from infected animals. Human-to-human transmission is through sustained close contact and direct contact with skin lesions. Materials that have been in contact with an infectious person (e.g., bedding) can also be a potential source of transmission. Spreading through respiratory droplets containing live virus may also be possible.
In the current outbreak, most cases have been isolated in men between the ages of 25-40 years who identify as gay, bisexual, or other men who have sex with men (GBMSM), with transmission occurring through close intimate contact. Mpox is not considered a sexually transmitted infection but an infection that is readily passed through close contact with infectious skin lesions.
Clinicians should remain open and non-judgmental when taking a sexual history and any other part of the medical history as part of the diagnostic work-up process.
What are the clinical features?
The incubation period has been documented as 6 to 13 days but may extend to as long as 21 days. Patients present with nonspecific symptoms such as fever, headaches, chills, malaise, myalgia, backache, and lymphadenopathy.
These are then followed by the typical vesicular rash. Previously, the rash has been described as starting in the mouth and then spreading to the face and extremities (including the palms and soles). However, in most current cases, the pox lesions have started in the genital, perianal and surrounding areas or on the hands, likely reflecting contact points with another person’s lesions. Typically, the lesions begin like chickenpox as macules and then go on to papules, vesicles, pustules, and finally scab over. Fortunately, the number of paediatric cases in the UK (<16) has been <0.5%. The lesions may be painful initially and tend to become itchy once in the healing phase. The number of lesions present can be anything between 10 and 100.
Like chickenpox, patients are infectious from when symptoms start (including that nonspecific prodromal period) until the lesions have healed and new skin has formed. Complications include bacterial superinfection, encephalitis, proctitis, conjunctivitis, tonsillitis, pharyngitis and pneumonitis. However, there is scanty evidence on the prevalence of developing complications in non-endemic developed countries, as this was a rare infection outside of central and western Africa before 2022.
Presently, the rates of such complications have been very low, with overall mortality estimated at less than 0.5%.
What should we do if we have a suspected case in our department?
Questions to ask yourself when considering a potential case of Mpox:
- Does your patient have a febrile prodrome compatible with Mpox in the context of an unexplained rash?
- Have they had contact with a confirmed case in the previous 21 days?
- Are they in an epidemiologically high-risk group (recent travel to Central/western Africa or GBMSM)?
- Or do you have a very high clinical suspicion based on a typical Mpox-like rash?
If suspected, think about how you can isolate the patient and then….
There needs to be a discussion with your local friendly infectious diseases clinicians. In the United Kingdom, there is a 24-hour Mpox helpline. Your local/national public health department should also be involved in suspected cases. If, after discussion, there is still ongoing suspicion, then you would need to test for the virus while performing other tests to figure out alternate diagnoses. Patients should be isolated, with HCPs wearing PPE as per local guidelines. If hospital admission is not needed, then they should self-isolate at home.
How can we test for it?
Firstly – protect yourself! The current recommendation is to use PPE against contact and droplet transmission. This includes eye protection. Check with your local infection prevention and control teams and see national advice in the UK from the National Infection Prevention and Control manual.
Diagnosis is made via PCR of a viral swab from one or more vesicles or ulcers. Swab the open wound or vesicle, then place it in the viral transport medium. You can also send a throat swab. This may be particularly useful during the prodromal phase. In the UK, samples should be sent to your local laboratory for forwarding to the Rare and Imported Pathogens Laboratory (RIPL).
It is important to think about alternate diagnoses and test for those, too.
Once a case has been confirmed, other tests may be requested for monitoring (repeat viral PCR swabs, urine and blood PCR).
What is the treatment?
There is no specific treatment for Mpox. Currently, the mainstay is supportive measures only, e.g. Time for a fluid shift? analgesia and maintaining fluid balance, given the potential multiple skin lesions. Then, the focus is on the treatment of complications. Novel antiviral medications such as Tecovirimat and Brincidofovir are sometimes used in severe cases under specialist guidance. In the UK and other countries, pre-exposure and post-exposure vaccination with the smallpox vaccine is being given to high-risk groups with the rationale that it will offer some cross-protection against Mpox.
When can a patient with Mpox stop isolating?
Advice on ending isolation will likely vary from country to country and change over time. Guidance (July 2022) from UKHSA suggests that patients with confirmed Mpox can de-isolate once fever-free for 72 hours have developed no new lesions for 48 hours, have no lesions in mucous membranes, and once all lesions have crusted over, and new skin is forming underneath. In some cases, laboratory evidence with repeat viral PCRs can help decision-making.
We must recognise the signs and symptoms of Mpox. This is a rapidly evolving multi-country epidemic. As such, guidance may quickly change. It is a global public health concern, allowing us to learn from others who have been dealing with this condition for many years.
It is important to note that this is a rapidly evolving epidemic; the information given here is liable to change as quickly as it is published!
References
Boghuma Titanji, MD, PhD, Bryan Tegomoh, MD, MPH, Saman Nematollahi, MD, MEHP, Michael Konomos, MS, CMI, Prathit A Kulkarni, MD, Monkeypox – A Contemporary Review for Healthcare Professionals, Open Forum Infectious Diseases, 2022;, ofac310, https://doi.org/10.1093/ofid/ofac310
GOV UK: Monkeypox guidance https://www.gov.uk/government/collections/monkeypox-guidance#guidance-for-health-professionals-and-service-providers
GOV UK: Monkeypox: diagnostic testing https://www.gov.uk/guidance/monkeypox-diagnostic-testing
GOV.uk : Monkeypox cases confirmed in England- latest updates https://www.gov.uk/government/news/monkeypox-cases-confirmed-in-england-latest-updates
Monkeypox 24-hour helpline UK: 0344 225 0602 (24 hours a day, medical practitioners only).
Monkeypox vaccination strategy https://www.gov.uk/guidance/monkeypox-outbreak-vaccination-strategy
National Infection protection and control manual https://www.england.nhs.uk/publication/national-infection-prevention-and-control/
WHO: Multi-country monkeypox outbreak in non-endemic countries https://www.who.int/emergencies/disease-outbreak-news/item/2022-DON385
