Mpox (formerly called monkeypox) is a disease that infects both humans and animals, namely rodents and non-human primates. It is caused by the monkeypox virus (MPXV), a DNA virus that belongs to the Orthopoxvirus genus, which also includes variola virus (the causitive agent of smallpox), vaccinia virus (the virus used in the smallpox vaccine) and cowpox virus. Notably, chickenpox, another pox-like disease that displays some similarities in symptomology, is caused by varicella-zoster virus and is not related to mpox.

Mpox is spread through direct person-to-person contact, either via respiratory droplets or exposure to infectious lesions or other bodily fluids. It may also be passed from mother to child and may be contracted by touching contaminated surfaces or handling infected animals, animal feces or bedding. Whether or not the virus can be sexually transmitted remains under investigation.

Mpox vs. Smallpox

Mpox Comparative Infographic
Source: American Society for Microbiology


The symptoms of mpox and smallpox are very similar. Both viruses cause fever, chills, headaches, muscle aches and fatigue, as well as a characteristic rash with fluid-filled lesions that are concentrated on the face, mouth and extremities. Notably, during the 2022 mpox outbreaks, increased oral and anogenital lesions have been reported.


The biggest differences between mpox and smallpox are that mpox has a much lower fatality rate and broader known host range than smallpox. Depending on the clade, mpox has a case fatality rate of 1-10%. While smallpox is fatal in 30-50% of cases, the fact that humans are the only known reservoir was instrumental in smallpox eradication in 1980.

Hear From Experts

What Is Mpox? How Do You Catch It and Is There a Vaccine?

An Intro to Monkeypox: From the Perspective of a Clinical Microbiologist, Reeti Khare, Ph.D., Clinical Microbiologist, National Jewish Health and author of Guide to Clinical and Diagnostic Virology joined the ASM Studio at ASM Microbe 2022 to answer pressing questions about the symptoms, transmission dynamics, prevention and treatment strategies and basic virology of the monkeypox virus

Mpox Clinical Update with Dr. Daniel Griffin

Mpox answers, including their origin, clinical presentation, diagnosis, treatment, and overall risk.

Neglected Tropical Diseases and Pandemic Prevention with Peter Hotez

The global impact and historical context of neglected tropical diseases.

Timeline of Outbreaks

Mpox Timeline
Source: American Society for Microbiology


  • 1958: mpox virus is first discovered among laboratory monkeys who exhibited pox-like disease.
  • 1970: the first human case of mpox is reported in the Democratic Republic of Congo (DRC) when a 9-month-old boy was found to be infected.
  • Following the first documented human case, mpox is reported in 11 different African countries.
  • The disease is considered endemic to Cameroon, the Central African Republic, DRC, Gabon, Ghana, Cote D’Ivoire, Liberia, Nigeria, the Republic of the Congo and Sierra Leone.
  • 2003: mpox is first reported in the U.S. Cases in non-endemic countries have been historically rare.
  • Jan 1-Sept. 13, 2020: approximately 4,594 suspected global cases of mpox and 171 deaths related to the virus are reported.
  • May 2022: reports of mpox outbreaks in non-endemic countries begin to circulate.
  • June 30, 2022: there are almost 400 confirmed cases of mpox in the U.S. (the largest outbreak in the country since 2003), nearly 1,200 cases reported in the U.K. and at least 29 other non-endemic countries reporting mpox cases.


Zoonotic diseases, those transmitted between humans and animals, account for 75% of new or emerging infectious diseases. Mpox is a zoonotic disease, highlighting the importance of predicting and preventing spillover events. The future of public health depends on this, particularly as interactions with wildlife and domestic animals increase.