Kris Kristofferson

Monkeypox is a viral zoonosis (a disease transmitted from animals to humans) that presents symptoms similar to those observed in smallpox patients, although it is clinically less severe. It is caused by the monkeypox virus, which belongs to the Orthopoxvirus genus within the Poxviridae family. Despite its name, the disease is not exclusively found in monkeys, and rodents are believed to be the primary reservoir of the virus.

Origins and History

Monkeypox was first discovered in 1958 when two outbreaks of a pox-like disease occurred in colonies of monkeys kept for research, hence the name "monkeypox." The first human case of monkeypox was recorded in 1970 in the Democratic Republic of Congo (DRC) during a period of intensified efforts to eliminate smallpox. Since then, monkeypox has been reported in humans in other central and western African countries. However, the DRC remains the country with the highest number of cases.

Historically, the majority of cases were reported in rural, rainforest regions of the Congo Basin, particularly in the DRC. Human monkeypox was rarely reported outside Africa until 2003, when an outbreak occurred in the United States, marking the first reported cases outside of the continent. The outbreak in the United States was linked to imported African rodents, which transmitted the virus to pet prairie dogs. This outbreak highlighted the potential for monkeypox to spread internationally.

Transmission

Monkeypox virus is primarily transmitted to humans from wild animals such as rodents and primates, but human-to-human transmission also occurs. The virus can spread through direct contact with the blood, bodily fluids, or cutaneous or mucosal lesions of infected animals. In Africa, evidence of monkeypox virus infection has been found in many animals, including rope squirrels, tree squirrels, Gambian pouched rats, dormice, primates, and others.

Human-to-human transmission occurs through close contact with respiratory secretions, skin lesions of an infected person, or recently contaminated objects. Transmission via droplet respiratory particles usually requires prolonged face-to-face contact, which puts household members and healthcare workers at greater risk. The virus can also be transmitted through the placenta from mother to fetus, which can lead to congenital monkeypox. There is also evidence that the virus can spread through contact with respiratory secretions, skin lesions, or objects recently contaminated with the virus, such as bedding or clothing.

Symptoms and Clinical Presentation

The incubation period (time from infection to symptoms) of monkeypox is usually 6 to 13 days but can range from 5 to 21 days. The infection can be divided into two periods:

1. The Invasion Period (0-5 days): Characterized by fever, intense headache, lymphadenopathy (swelling of the lymph nodes), back pain, myalgia (muscle aches), and an intense asthenia (lack of energy). Lymphadenopathy is a distinctive feature of monkeypox compared to other diseases that may initially appear similar (chickenpox, measles, smallpox).

2. The Skin Eruption Period (within 1-3 days after the appearance of fever): The various stages of the rash appear, often beginning on the face and then spreading to other parts of the body. The face (95% of cases), palms of the hands, and soles of the feet (75% of cases) are most affected. The rash evolves from macules (flat lesions) to papules (slightly raised, firm lesions), vesicles (fluid-filled lesions), pustules (pus-filled lesions), and finally crusts that fall off. The number of lesions varies from a few to several thousand. In severe cases, lesions can coalesce until large sections of skin slough off.

Monkeypox is usually a self-limited disease with symptoms lasting from 2 to 4 weeks. Severe cases occur more commonly among children and are related to the extent of virus exposure, patient health status, and the nature of complications. Underlying immune deficiencies may lead to worse outcomes. Although vaccination against smallpox has been shown to be about 85% effective in preventing monkeypox, prior to the recent resurgence of monkeypox, there was no widespread vaccination against smallpox, leading to an increase in susceptible populations.

Complications

Complications of monkeypox can include secondary bacterial infections, bronchopneumonia, sepsis, encephalitis, and corneal infection with subsequent loss of vision. The extent to which a person can develop severe complications depends on several factors, including the strain of the virus, the health of the individual, and the quality of medical care available.

Historically, the case fatality ratio of monkeypox has varied between 0 and 11% in the general population and has been higher among young children. In recent times, the case fatality ratio has been around 3 to 6%.

Diagnosis

Diagnosis of monkeypox can be challenging due to its similarity to other rash-causing illnesses, such as chickenpox, measles, bacterial skin infections, scabies, syphilis, and medication-associated allergies. The clinical differential diagnosis is broad and depends on the patient’s age, health history, and the prevalence of other diseases that cause similar symptoms.

Confirmation of monkeypox requires laboratory testing. Polymerase chain reaction (PCR) is the preferred laboratory test due to its accuracy and sensitivity. The best diagnostic samples for monkeypox are from skin lesions – the roof or fluid from vesicles and pustules, and dry crusts. Blood is not an optimal sample due to the brief duration of viremia (presence of viruses in the blood) compared to the timing of specimen collection after symptoms begin.

Treatment and Vaccination

There is currently no proven, safe treatment for monkeypox virus infection. The management of monkeypox is mainly supportive and symptomatic. The need for supportive care varies according to the severity of the case and the presence of complications. This may include managing secondary bacterial infections, providing hydration, and treating specific complications as they arise.

In 2019, the U.S. Food and Drug Administration (FDA) approved tecovirimat, an antiviral that was originally developed for smallpox, for the treatment of monkeypox based on data from animal and human studies. However, its effectiveness in treating monkeypox in clinical settings is still being evaluated.

Vaccination against smallpox has been shown to provide cross-protection against monkeypox. In 2022, during the global outbreak, a newer vaccine, based on a modified vaccinia Ankara virus (a non-replicating virus), was used to prevent both smallpox and monkeypox. The newer vaccine is known as MVA-BN (marketed as Jynneos, Imvanex, or Imvamune). It is approved for the prevention of both smallpox and monkeypox and is being used in a ring vaccination strategy (vaccinating contacts and contacts of contacts) to help control outbreaks.

Epidemiology

Monkeypox is endemic to Central and West African countries, with the highest incidence in the DRC. The virus can spill over from animals to humans sporadically, causing outbreaks, particularly in areas where people live near forested areas where the animal hosts reside.

The 2003 U.S. outbreak was a significant event in the epidemiology of monkeypox, demonstrating that the disease could spread outside of Africa under the right conditions. The outbreak involved 47 confirmed and probable cases, all linked to contact with pet prairie dogs that had been housed with infected African rodents. This event emphasized the importance of controlling the international trade of exotic animals to prevent zoonotic diseases.

In 2017, Nigeria experienced its largest documented outbreak, 40 years after the last confirmed cases. This resurgence raised questions about the changing epidemiology of the disease, including the possibility of changes in the virus's transmission dynamics or an increase in susceptibility among the population.

The 2022 Global Outbreak

In May 2022, an unprecedented outbreak of monkeypox was reported across multiple countries where the virus is not endemic, including Europe, North America, and beyond. The outbreak primarily affected men who have sex with men (MSM), particularly those with multiple sexual partners. Unlike previous outbreaks, the majority of cases occurred in urban settings, and human-to-human transmission appeared to be the main mode of spread.

The rapid spread of monkeypox during this outbreak raised concerns about the potential for the virus to establish itself outside of Africa, leading to ongoing transmission. It also highlighted the challenges of controlling the spread of zoonotic diseases in an interconnected world, where international travel and trade can facilitate the spread of pathogens.

In response to the 2022 outbreak, the World Health Organization (WHO) declared monkeypox a Public Health Emergency of International Concern (PHEIC) in July 2022. This designation is intended to prompt coordinated international action to contain the spread of the virus.

Public Health Response and Challenges

Containing monkeypox outbreaks requires a multifaceted public health response, including surveillance, rapid diagnosis, contact tracing, isolation of cases, and vaccination. Public health authorities must also address the challenges of communicating risks to the public, particularly in the context of the 2022 outbreak, where misinformation and stigma posed significant barriers to effective communication and intervention.

Vaccination plays a crucial role in controlling monkeypox outbreaks, especially in populations at high risk of exposure. However, the availability of vaccines is limited, and there are logistical challenges in distributing them effectively. Moreover, the vaccine's side effects and efficacy must be carefully monitored.

The control of zoonotic diseases like monkeypox also requires a One Health approach, which recognizes the interconnectedness of human, animal, and environmental health. Preventing future outbreaks will require better understanding and monitoring of the animal reservoirs of the virus, as well as measures to reduce human-animal contact, particularly in areas where the virus is endemic.

Conclusion

Monkeypox is a re-emerging zoonotic disease with significant public health implications. Its ability to spread across borders and affect diverse populations highlights the need for vigilant surveillance, research, and public health preparedness. The 2022 global outbreak underscored the potential for monkeypox to become a significant global health threat, especially in populations with little or no immunity to orthopoxviruses.

Continued research is needed to understand the changing epidemiology of monkeypox, particularly in the context of the 2022 outbreak. There is also a need to improve the availability of diagnostic tools, treatments, and vaccines, particularly in resource-limited settings where the disease is endemic.

The recent resurgence of monkeypox serves as a reminder of the importance of global health security and the need for coordinated international efforts to prevent and control the spread of zoonotic diseases. In an increasingly interconnected world, the emergence and re-emergence of diseases like monkeypox will continue to pose challenges that require innovative and collaborative solutions.