Just like Covid-19, Monkeypox (MP) is caused by a virus (this time related to smallpox), but there are major differences between these 2 diseases. ^1-11

First, in contrast to Covid-19 which can easily be transmitted by casual contact through air, MP is primarily transmitted by close skin-to-skin contact (or possibly through contaminated clothing/bed linens) and sexual contact,  with great majority of current cases occurring among men who have sex with men (MSM); airborne transmission does not appear to be an important source of spread. ²

Although there is an overlap, the incubation period of MP tends to be longer (3-17 days) than that of Covid-19 which can be as few as 2 days.  Common to both diseases are flu-like symptoms such as fever, chills, muscle aches and headache, but MP is characterized by a rash that may be located on or near the genitals or anus or other areas, including hands, feet, chest face or mouth. ⁴

The rash (Figure) can look like pimples or blisters initially and may be painful or itchy as well. MP rash can either precede or follow flu-like symptoms after 1-4 days, or be the sole manifestation of the disease. Lymph node swelling or eye involvement (advise infected patients not to touch their eyes) may occur.  Although respiratory symptoms such as sore throat, nasal congestion and cough may occur with both diseases, shortness of breath would be unusual in MP.  A person with MP is considered contagious from onset of illness until the rash scabs over completely, which usually takes 2-4 weeks. ^4,5,7,8

In contrast to Covid-19, currently there are no specific proven effective therapy against MP. However, several therapeutic agents with known activity against smallpox may be considered for those particularly at high risk of complications (eg, immunosuppressed patients, those with severe disease, exfoliative skin conditions [eg, eczema, psoriasis, Darier disease] children <8 years of age, pregnant or breast feeding patients, those with complications {eg, bacterial skin infection, pneumonia, gastroenteritis) or concurrent comorbidities.  These include an antiviral drug, Tecovirimat (TPOXX, ST-246) which can be obtained under an expanded-access protocol through the CDC in the U.S. (https://www.cdc.gov/poxvirus/monkeypox/clinicians/obtaining-tecovirimat.html. opens in new tab) — and Vaccinia Immune Globulin Intravenous (VIGIV) also through the CDC. ^3,10

There are some “good news” related to MP when compared to Covid-19. First, in contrast Covid-19, hospitalization or death from MP due to the current circulating West African strain of the virus are extremely uncommon to rare.   In fact, of more than 12,000 cases of MP in 68 countries during the first few weeks of the epidemic, only 3 deaths have been reported, none in the U.S. thus far. ²

Second, in contrast to Covid-19, a person with MP is not considered infectious before onset of symptoms. So from a public health standpoint, it may be easier to control the spread of MP in the population following identification of a case. ⁹

Third, vaccination of contacts with one of the 2 available vaccinia/smallpox vaccines following significant exposure to MP may prevent disease altogether or render the disease milder. Vaccines should be administered within 4 days of exposure and no longer than 14 days after.  The generally preferred vaccine against MP is a modified vaccinia virus Ankara vaccine (MVA; JYNNEOS in the U.S., Imvanex in the European Union, and Imamune in Canada) which is live but non-replicative and is associated with fewer adverse events and contraindications than the alternative, ACAM2000, a live smallpox vaccine. ³

Last, in contrast to lack of pre-existing immunity to Covid-19 in virtually everyone  when the pandemic hit over 2 years ago, a large proportion of the population who received smallpox vaccine as part childhood vaccination (ending in 1972 in the U.S.) may have at least partial immunity against MP, resulting in either no or milder disease.^6,11  

Bonus Pearl: Did you know that despite its name, monkeys are not a natural host of Monkeypox, with the causative virus having been isolated from a wild monkey in Africa only once? Instead, the virus first got its name after it was identified in a colony of Asian monkeys in a laboratory in Denmark in 1958. Squirrels, rats and shrew species serve as its natural host.¹

Figure: Monkeypox rash (Courtesy CDC). 

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References

1. Cohen J. Monkeypox is a new global threat. African scientists know what the world is up against. Science. June 1 2022. Monkeypox is a new global threat. African scientists know what the world is up against | Science | AAAS
2. Osterholm MT. Gellin B. Confronting 21^st-century monkeypox. Science 2022;377:349. Confronting 21st-century monkeypox | Science
3. Medical countermeasures available for the treatment of monkeypox. Treatment Information for Healthcare Professionals | Monkeypox | Poxvirus | CDC. Accessed August 2, 2022.
4. Key characteristics for identifying monkeypox. Clinical Recognition | Monkeypox | Poxvirus | CDC. Accessed August 6, 2022
5. Monkeypox signs and symptoms. Signs and Symptoms | Monkeypox | Poxvirus | CDC. Accessed August 6, 2022.
6. Karem KL, Reynold M, Hughes C, et al. Monkeypox-induced immunity and failure of childhood smallpox vaccine to provide complete protection. Clin Vaccine Immunol 2007;14:1318-27. Monkeypox-induced immunity and failure of childhood smallpox vaccination to provide complete protection – PubMed (nih.gov)
7. Monkeypox: Key facts. Monkeypox (who.int). Accessed August 6, 2022.
8. Clinical presentations of Covid-19. Clinical Presentation | Clinical Care Considerations | CDC. Accessed August 6, 2022.
9. How monkeypox spreads. How it Spreads | Monkeypox | Poxvirus | CDC. Accessed August 6, 2022.
10. Sherwat A, Brooks JT, Birnkrant D, et al. Tecovirimat and the treatment of monkeypox—past, present, and future. N Engl J Med 2020. August 3, 2022. Tecovirimat and the Treatment of Monkeypox — Past, Present, and Future Considerations | NEJM
11. Mandavilli A. Who is protected against monkeypox. NY Times. May 26, 2022. Who Is Protected Against Monkeypox? – The New York Times (nytimes.com)

Disclosures: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Mercy Hospital-St. Louis, Massachusetts General Hospital, Harvard Catalyst, Harvard University, their affiliate academic healthcare centers, or its contributors. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!