Mpox (monkeypox): causes, symptoms, treatment and prevention

The World Health Organization (WHO) declared on August 14, 2024 that monkeypox virus infection constitutes a public health emergency of international concern amid rapidly increasing infections in East and Central Africa and a high risk of global spread. The incidence of confirmed cases is 160% higher than last year and with a 19% higher mortality rate (The Johns Hopkins University, 2024) The novel variant circulating at this time is thought to be highly contagious and aggressive.

The first European country to confirm a case of infection with this virus was Sweden (August 15, 2024), where the person was infected with subclade Ib following a trip to Africa in an area with many mpox cases. In 2022, a few cases of monkeypox (mpox) were reported in Romania, but they were mild forms.

What is monkeypox (mpox)?

Mpox (formerly known as monkeypox) is a disease caused by infection with monkeypox virus (MPXV), an encapsidated virus belonging to the genus Orthopoxvirus in the family Poxviridae. This genus also includes vaccinia virus, cowpox virus, smallpox virus and several other pathogenic animal poxviruses (International Committee on Taxonomy of Viruses, 2009).

There are two genetically distinct strains/clades of the virus: clade I (formerly called Congo Basin-Central Africa clade), with subclades Ia and Ib, and clade II (formerly called West African clade), with subclades IIa and IIb (Likos, et al., 2005) (Team, 2022). Clade I has been associated with more severe symptoms and higher mortality – 3.6% compared to 0.2% in clade 2, which was the clade that caused the 2022 global outbreak originating in West Africa (McCollum & Damon, 2013) (McCollum & Damon, 2013).

Poxviruses have long-lasting stability in the environment (exhibit greater tolerance to drying, temperature, and pH) (Essbauer, Meyer, Porsch-Ozcürümez, & Pfeffer, 2007), and MPXV can be detected on household surfaces even 15 days after contamination (Morgan, et al., 2022). However, it is sensitive to common disinfectants, but less sensitive to organic ones.

The virus that causes mpox was discovered in Denmark in 1958 after two outbreaks of a smallpox-like disease, hence the original name ‘monkeypox’, occurred in several monkey colonies used for research. But the exact source is not known, and it may also be African rodents and infect humans.

The first human case of mpox was recorded in 1970, in what is now the Democratic Republic of Congo, nine months after the eradication of smallpox in that country (Giulio & Eckburg, 2004). In 2022 it spread worldwide, usually until then there had been isolated cases that were linked to travel to endemic regions and imports of animals from these areas (WHO, 2024). In the same year, the WHO renamed the disease mpox to follow modern guidelines for disease names. These recommend that “disease names should avoid offending cultural, social, national, national, regional, occupational or ethnic groups and minimize unnecessary adverse effects on trade, travel, tourism or animal welfare”. However, the virus retains its name. (***, About Mpox, 2024)

How is it transmitted?

MPXV is transmitted by prolonged close physical contact with an infected human or animal (even by scratching, biting or eating meat) or by contact with contaminated materials. The virus enters the body through injured skin or mucous membranes as follows: (***, Mpox – How It Spreads, 2024)

  • Direct contact with rash or scabs from an infected person
  • Direct face-to-face contact with saliva, respiratory droplets, body fluids or lesions around the anus, rectum or vagina
  • Intimate contact (sexual intercourse, touching the genitals, hugging, massaging, kissing): however, this is not considered a sexually transmitted disease
  • Touching contaminated and uninfected objects and textiles (bed linen, towels, etc.)
  • During and immediately after childbirth (Mbala, et al., 2017)
  • Nosocomial infections (Likos, et al., 2005)

Evidence indicates that infected people can transmit the virus up to four days before the onset of symptoms (Brosius, et al., 2022). A UK study showed that 53% of transmission occurred in the pre-symptomatic period (Ward, Christie, Paton, Cumming, & Overton, 2022).

The infectious period ends when all skin lesions develop a crust and reepithelialization occurs (Mitjà, et al., 2023).

In studies, the percentage of positive samples was found to decrease substantially within a period of three weeks to 40 days after the onset of symptoms (Palich, et al., 2023) (Suñer, et al., 2023). People with severe HIV infection have a more extended period of illness. (O, et al., 2023)

There have been cases when between 1.3% and 6.5% of infected people never showed symptoms (Agustí, et al., 2023). The incubation period is usually between 6 and 13 days, but can range from 5 to 21 days.

Which people are most at risk of infection?

Anyone who has prolonged close contact with an infected person is at risk of becoming infected, but there are certain categories of people who are more likely to become infected: people who live with an infected person, healthcare workers who may come into contact with infected patients, people who provide sexual services, and men who have sex with men. (WHO, 2024)

What are the signs and symptoms?

The duration of signs and symptoms is estimated to be between 2 to 4 weeks.

The disease starts with nonspecific symptoms such as fever, chills, headache, back pain (lumbago) and muscle pain (myalgia), asthenia, lethargy. Adenopathy (enlargement and swelling of the lymph nodes) is a characteristic symptom of this infection that distinguishes it from others with similar symptoms and occurs in up to 90% of patients. (Petersen, et al., 2019)

After 1 to 3-5 days after the onset of fever, rashes of various sizes appear, first on the face, hands (including palms) or feet (including soles) and then on the rest of the body. In the 2022 outbreak, the rash usually started in the genital area, mouth or throat (Tosh, 2024). The rash progresses through several stages: macules (lesions with a flat base: lasts 1-2 days), papules (firm, slightly raised lesions: lasts 1-2 days), vesicles (fluid-filled lesions: lasts 1-2 days) and pustules (lesions filled with yellowish fluid: lasts 5-7 days). Then scabs appear, which dry and fall off over a period of 7 to 14 days. Their number varies from a few to hundreds or more, and in more severe cases, they may coalesce until large areas of skin break off. (Petersen, et al., 2019)

In some cases, inflammation of the cornea, conjunctival, pharyngeal and genital mucosa, pain, and difficulty urinating or swallowing may be seen (WHO, 2024).

Mortality is higher in children and young adults, and the course is more severe in immunosuppressed people.

When to go to the doctor?

You should contact your GP if you feel unwell and:

  • you have fever, aches or swollen lymph nodes
  • have a new rash or sores
  • you have been in close contact with an infected person

Contact the emergency department if they occur (***, Mpox, 2023):

  • difficulty breathing
  • new or worsening chest pain
  • difficulty speaking or moving
  • confusion
  • stiff neck
  • seizures
  • loss of consciousness

How can it be diagnosed?

Identifying mpox can be difficult because other infections have similar symptoms: chickenpox, measles, bacterial skin infections, scabies, drug allergies or sexually transmitted diseases (herpes, syphilis). A patient can be infected with multiple pathogens at the same time (e.g. mpox and chickenpox), so testing is essential for early diagnosis and correct treatment (WHO, 2024). Usually, swollen lymph nodes indicate that we are talking about mpox, but a lab test will demonstrate this.

The most appropriate is PCR (detection of viral DNA by polymerase chain reaction). Samples are taken directly from skin lesions (skin, fluid or scabs) by vigorous swabbing. In their absence, sampling may be done by swabbing the throat or anus. (WHO, 2024).

Blood testing is not recommended as it does not distinguish between orthopoxviruses.

Additional testing for HIV, varicella-zoster virus, herpes is also recommended. (WHO, 2024).

What are the complications?

People at higher risk of developing complications are:

  • Those who are immunosuppressed
  • Those with a history of eczema
  • Pregnant women
  • Children under one year of age

Possible complications that can occur are secondary infections of the skin (leading to abscesses or lesions), blood (sepsis) or cornea (with loss of vision), inflammation of the brain (encephalitis), heart (myocarditis), rectum (proctitis), genitals (balanitis), urinary tract (urethritis), vomiting and diarrhea (with severe dehydration or malnutrition), respiratory distress, bronchopneumonia and in severe cases, even death. (WHO, 2024).

Mortality rates have ranged between 1% and 10% in outbreaks, with deaths occurring mainly among children and young adults, with the immunocompromised at risk of severe disease. (Petersen, et al., 2019)

What is the treatment?

Mpox is usually a self-limiting disease (it gets better without treatment), but your doctor may still prescribe antithermics, pain relievers, vitamins and ointments to relieve certain symptoms and prevent dehydration (by drinking fluids) (***, Clinical Treatment, 2024). (***, Clinical Treatment, 2024)

In more severe forms, patients will be hospitalized and given antiviral medication, and if secondary bacterial infections occur, certain antibiotics may need to be given.

How do we prevent illness?

Previous smallpox vaccination confers some cross-protection against monkeypox, with milder symptoms, but this is true for people who received this vaccine before 1980, when smallpox was eradicated and mass vaccination stopped.

One of the vaccines approved in Europe for the prevention of both smallpox and mpox is JYNNEOS®, a third-generation vaccine that can be used from 2019. It, also known as Imvamune® or Imvanex® internationally, was approved in August 2022 by the US Food and Drug Administration (FDA) for use against mpox intradermally (requires a lower dose of vaccine – 0.1 ml) in people over 18 years of age and subcutaneously (0.5 ml) in those under 18 years of age. (***, JYNNEOS-Frequently Asked Questions )

Vaccines for smallpox and mpox can be used in two situations: pre-exposure to prevent infection or post-exposure to ameliorate the disease. Pre-exposure vaccination is designed to protect those at highest risk of infection. Post-exposure vaccination is ideally given within 4 days of exposure to prevent infection, but can be used up to 14 days after exposure to decrease disease severity (Poland, Kennedy, & Tosh, 2022). For both types of vaccination, the greatest protection is conferred by a second or third generation vaccine.

According to health experts, none of the approved vaccines are recommended to be given en masse, but only if deemed necessary following a proper medical evaluation.

The most practical prevention methods are to follow general hygiene rules and avoid contact with contaminated people or animals:

  • After using the toilet, before eating, and after contact with other people or possibly contaminated surfaces or textiles, it is recommended that hands be washed with soap and water and a hand sanitizer be used, alcohol-based hand sanitizer being a good choice;
  • Disinfect possibly contaminated surfaces;
  • Avoid traveling to endemic areas;
  • If a person is suspected of being infected with monkeypox virus, they should be isolated. If it is necessary to have another person around the patient, cover the patient’s lesions, wear a mask and gloves, and finally disinfect properly. (***, Isolation & Infection Control at Home, 2022)

Early identification of mpox cases through correct diagnosis, isolation of infected persons, starting treatment, identification and close monitoring of contacts are the effective methods by which the spread of the disease can be controlled.

Note: The information in this article is for information purposes only. If you have specific symptoms, contact your family doctor for advice.

Photo source: Shutterstock

Sources:

***. Retrieved from chrome-extension://efaidnbmnnnnnibpcajpcglglclefindmkaj/https://www.nj.gov/health/monkeypox/documents/Vaccination/jynneos_faq.pdf

***. (Retrieved from https://www.cdc.gov/poxvirus/mpox/clinicians/infection-control-home.html#hand-hygiene

***. (2023). Retrieved from https://my.clevelandclinic.org/health/diseases/22371-monkeypox#overview

***. (2024). Retrieved from https://www.cdc.gov/poxvirus/mpox/about/index.html

***. (2024). Retrieved from https://www.cdc.gov/poxvirus/mpox/if-sick/transmission.html

Agustí, C., Martínez-Riveros, H., Hernández-Rodríguez, À., Casañ, C., Díaa, Y., Alonso, L., & al, e. (2023).

Brosius, I., Dijck, C. V., Coppens, J., Vandenhove, L., Bangwen, E., Vanroye, F., . . Griensven, J. v. (2022). Pre- and asymptomatic viral shedding in high-risk contacts of monkeypox cases: a prospective cohort study.

Essbauer, S., Meyer, H., Porsch-Ozcürümez, M., & Pfeffer, M. (2007). Long-lasting stability of vaccinia virus (orthopoxvirus) in food and environmental samples. Zoonoses Public Health, 1863-2378.

Giulio, D. Human monkeypox: an emerging zoonosis. The Lancet: Infectious Diseases, 15-25.

International Committee on Taxonomy of Viruses (2009). Retrieved from https://ictv.global/report_9th/dsDNA/poxviridae

Likos, A. M., Sammons, S. A., Olson, V. A., Frace, A. M., Li, Y., Olsen-Rasmussen, M., . . . Formenty, P. e. (2005). A tale of two clades: monkeypox viruses. The Journal of general virology, 86, 2661-2672.

Mbala, P. K., Huggins, J. W., Riu-Rovira, T., Ahuka, S. M., Mulembakani, P., Rimoin, A. W., . . . Muyembe, J.-J. T. (2017) Maternal and Fetal Outcomes Among Pregnant Women With Human Monkeypox Infection in the Democratic Republic of Congo. The Journal of Infectious diseases, 824-828.

McCollum, A. M., & Damon, I. K. (2013). human monkeypox. Clinical Infectious Diseases, 58, 260-267. Retrieved from https://academic.oup.com/cid/article/58/2/260/335791?login=false

Mitjà, O., Ogoina, D., Titanji, B. K., Galvan, C., Muyembe, J.-J., Marks, M., & Orkin, C. M. (2023). Monkeypox. Lancet (London, England), 60-74.

Morgan, C. N., Whitehill, F., Doty, J. B., Schulte, J., Matheny, A., Stringer, J., . . . McCollum, A. M. (2022). Environmental Persistence of Monkeypox Virus on Surfaces in Household of Person with Travel-Associated Infection, Dallas, Texas, USA, 2021. Emerging Infectious Diseases, 1982-1989.

O, M., A, A., M, M., JI, L. M., JC, R.-A., MS, T. S., & al., e. (2023). Mpox in people with advanced HIV infection: a global case series. Lancet (London, England), 939-949.

Palich, R., Burrel, S., Monsel, G., Nouchi, A., Bleibtreu, A., Seang, S., . . . al., e. (2023). Viral loads in clinical samples of men with monkeypox virus infection: a French case series. The Lancet. Infectious diseases, 74-80.

Petersen, E., Kantele, A., Koopmans, M., Asogun, D., Yinka-Ogunleye, A., Ihekweazu, C., & Zumla, A. (2019). Human Monkeypox: Epidemiologic and Clinical Characteristics, Diagnosis, and Prevention. Infectious Disease Clinics of North America, 1027-1043.

Poland, G. A., Kennedy, R. B., & Tosh, P. K. (2022). Prevention of monkeypox with vaccines: a rapid review. The Lancet Infectious Diseases, 349-358.

Suñer, C., Ubals, M., Tarín-Vicente, E. J., Mendoza, A., Alemany, A., Hernández-Rodríguez, Á., . . . al, e. (2023). Viral dynamics in patients with monkeypox infection: a prospective cohort study in Spain. The Lancet: Infectious diseases, 445-453.

Team, W. M. (2022). Retrieved from https://www.who.int/news/item/12-08-2022-monkeypox–experts-give-virus-variants-new-names

Tosh, P. K. (2024). Retrieved from https://www.mayoclinic.org/.

Ward, T., Christie, R., Paton, R. S., Cumming, F., & Overton, C. E. (2022). Transmission dynamics of monkeypox in the United Kingdom: contact tracing study. BMJ (Clinical research ed).

WHO. (2024). Retrieved from https://www.who.int/news-room/fact-sheets/detail/mpox