2022 Global Mpox Outbreak
The first global mpox outbreak outside Africa — 87,000+ cases in 110+ countries, a WHO PHEIC, and a new understanding of mpox as a sexually transmissible infection.
Outbreak Summary
| Metric | Data |
| First case (2022 global) | UK, May 7, 2022 |
| WHO PHEIC declared | July 23, 2022 |
| WHO PHEIC ended | May 11, 2023 |
| Total global cases | >87,000 (110+ countries) |
| Deaths | ~140 |
| Clade | Clade IIb (West African clade, new sub-lineage) |
| Primary transmission | Close sexual contact (predominantly MSM networks) |
Timeline
- May 7, 2022: UK detects first case (returned traveler from Nigeria)
- May 13–21, 2022: Cases identified in Portugal, Spain, Canada, USA — community transmission confirmed
- May 20, 2022: WHO emergency meeting; cases in 12 countries
- Jul 23, 2022: WHO Director-General declares PHEIC (overriding Emergency Committee non-consensus)
- Aug 2022: Cases peak globally; US declares public health emergency; JYNNEOS vaccination expands
- Sep–Oct 2022: Cases decline sharply in Europe and North America
- Nov 2022: US cases below 100/week; epidemic controlled in most high-income countries
- May 11, 2023: WHO ends PHEIC
What Changed: Mpox as an STI
The 2022 outbreak fundamentally changed scientific and clinical understanding of mpox. Prior understanding was that mpox spread through close physical contact, shared bedding, or respiratory droplets — not primarily sexual contact. The 2022 Clade IIb outbreak revealed that genital and perianal lesions were extremely common (often the first presentation), that rectal pain and proctitis were frequent symptoms, and that the virus was spreading efficiently through sexual networks among men who have sex with men. Viral DNA was found in semen, anal swabs, and rectal samples. This changed public-health information: sexual health clinics became the primary response hub, contact tracing adapted sexual health models, and vaccination targeting used HIV/sexual health registries. The outbreak demonstrated that an ancient poxvirus could adapt to new transmission patterns in a non-immune global population.
Sources: WHO global mpox situation data; ECDC mpox outbreak data; Lancet (Thornhill et al. 2022 clinical presentation); Nature Medicine genomic analyses 2022 Clade IIb.
Related: Mpox overview · USA mpox · 2024 Clade Ib outbreak
Vaccine Response: JYNNEOS and the Intradermal Innovation
JYNNEOS (also branded Imvamune or Imvanex), a modified vaccinia Ankara vaccine authorized for both smallpox and mpox, became the primary vaccination tool in 2022. Supply was critically limited at outbreak start — only approximately 100,000 doses immediately available in the US in June 2022, against potentially hundreds of thousands of exposed high-risk individuals. In August 2022, FDA authorized intradermal vaccination using one-fifth the dose per vial injection, effectively expanding available supply five-fold from existing stocks. This single regulatory decision allowed vaccination of millions rather than hundreds of thousands of high-risk individuals during the critical outbreak window. Evidence for JYNNEOS effectiveness came from observational studies: UK UKHSA and US CDC analyses found approximately 66–84% effectiveness against mpox infection after two doses, with meaningful partial protection after a single dose — providing public health cover while manufacturing ramped up.
Stigma and Community-Led Response
The 2022 mpox outbreak generated significant stigma challenges. Media framing of mpox as exclusively a "gay disease" led to discrimination reports and, critically, deterred some at-risk individuals from seeking testing or vaccination. Public health communicators faced the genuine tension between accurately communicating epidemiological facts (gay and bisexual men were the most affected population in 2022) and preventing stigma that would undermine the response. The most effective responses — in San Francisco, New York, London, and Amsterdam — centered community organizations already trusted by MSM populations. LGBTQ+ health organizations, HIV service organizations, and sexual health clinics became the primary vaccination and testing hubs, with community leaders as spokespeople. The episode renewed discussion about health communication frameworks that prioritize community partnership over top-down messaging, particularly when outbreaks disproportionately affect populations with prior experience of healthcare stigma.
What Clade IIb Changed in Mpox Science
The 2022 outbreak generated a substantial body of new scientific knowledge about mpox transmission, clinical presentation, and epidemiology. Before 2022, mpox was understood primarily as a zoonotic disease with limited human-to-human spread. The Clade IIb outbreak revealed: genital and perianal lesions as primary presentation rather than centrifugal rash; rectal pain, proctitis, and genital ulcers as early symptoms; viral DNA detectable in semen; efficient spread through sexual skin-to-skin contact without requiring direct lesion-to-lesion contact; and a significant proportion of cases occurring in immunocompromised individuals (particularly those with HIV) who experienced more severe disease. These discoveries reshaped clinical screening criteria, diagnostic testing algorithms, and disease guidance and public-health references — including the use of tecovirimat (TPOXX) in severe cases, despite limited prospective trial data.