Unraveling Mpox: Insights from a Microbiologist on This Smallpox Relative

On August 14, 2024, the World Health Organization (WHO) announced mpox as a public health emergency of international concern. This declaration comes amidst alarming figures: over 15,600 confirmed cases and more than 530 fatalities reported primarily in the Democratic Republic of the Congo and surrounding countries. A previous global outbreak of the disease spanned from 2022 to 2023.

Mpox, formerly known as monkeypox, has been recognized since the first human case was documented in 1970. This case occurred in the DRC, where the virus was isolated from a child suspected of having smallpox. While typically mild, mpox can lead to severe health issues, especially with rising international travel.

The mpox virus is a member of the Orthopoxvirus genus within the Poxviridae family, which also includes smallpox, vaccinia, and cowpox viruses. While the precise animal reservoir remains unidentified, African rodents are suspected carriers. Diagnostic testing for mpox is currently accessible only through Laboratory Response Network labs across the U.S. and internationally.

The term “monkeypox” originated from the first recorded animal cases in 1958 during outbreaks in monkeys used for research. Notably, the virus’s transition from monkeys to humans has never been established, nor are monkeys key carriers of this disease.

After its initial identification in humans, mpox has since been detected in various central and western African nations, predominantly in the DRC. Cases outside Africa typically arise from international travel or imported animals; the first U.S. outbreak was linked to a shipment of animals from Ghana in 2003. A resurgence began in May 2022, leading to the ongoing outbreak.

The smallpox vaccine, a significant defender against mpox, is no longer routinely administered to the general U.S. population since smallpox was declared eradicated in 1972. Consequently, there has been an uptick in mpox cases among unvaccinated individuals.

Transmission occurs mainly through contact with infected persons, animals, or contaminated surfaces. The virus often enters through broken skin, inhalation, or mucous membranes. Research indicates that human-to-human transmission primarily happens through large respiratory droplets rather than bodily fluids or clothing.

Health officials express concern about potential undetected community transmission, as investigations continue into the specific mechanisms and locations of ongoing infections.

Typically, mpox symptoms manifest one to two weeks post-infection. Initial signs resemble flu-like symptoms, including fever, headache, and shortness of breath. Following this, rashes can develop, leading to pus-filled blisters on various body parts. While the illness duration ranges from two to four weeks, skin lesions usually scab within 14 to 21 days.

Although mpox is generally rare and nonfatal, a more severe strain has a fatality rate of about 10%. The currently circulating variant appears milder, with a fatality rate below 1%.

Currently, there are no specific treatments for mpox; care focuses on symptom relief. The Centers for Disease Control and Prevention (CDC) reports that vaccination with the smallpox vaccine may offer protective benefits against mpox and lessen symptom severity. The U.S. has authorized a vaccine, Imvamune (or Imvanex), specifically for mpox and smallpox prevention.

Post-exposure vaccination could also reduce the risk of severe illness, particularly among immunocompromised individuals. The CDC recommends smallpox vaccination for those who have been or are likely to be exposed to mpox.