Update on Worldwide Monkeypox Outbreak, Including Epidemiology and Clinical Manifestations

Monica Gandhi, MD, MPH


July 28, 2022

I previously reported on the history of the current outbreak of monkeypox among mainly men who have sex with men (MSM) and the need to vaccinate MSM as soon as possible. I also discussed public health messaging around monkeypox and COVID and the need to increase trust in public health in this current time of infectious disease outbreaks. Now that the World Health Organization (WHO) has declared monkeypox a global health emergency of international concern (as of July 23), I wanted to provide you with an update on epidemiology, clinical manifestations, and vaccine strategy.

A very important clinical series was just published on July 21 in The New England Journal of Medicine that gives us a better idea of the most prevalent symptoms.

As a reminder, the first case of monkeypox was reported to the WHO on May 13, 2022. At this point, surveillance has revealed that almost 14,000 cases in the current outbreak have been reported in 78 countries. Most of the initial cases were in Europe, particularly in the UK, where the first European case was reported, but since then transmission has been reported across the world. The countries most affected are Spain, Germany, the United States, England, and France.

In the US, there have been 2891 cases reported as of July 23, 2022, with a high concentration in New York, followed by California. In California, there have been 434 cases reported as of June 23, with approximately one third of those in San Francisco, where I practice.

Most of the cases in this current outbreak are among men (with the worldwide surveillance site from Global Health showing that 99% of cases are in men) and the average age of individuals in this outbreak is 41 years. The major population at risk remains MSM, likely from close skin-to-skin contact and close respiratory contact.

In terms of the main clinical symptoms, an important case series was published in the NEJM this past week which describes the main clinical features of monkeypox in this outbreak. Among 528 cases diagnosed between April 27 and June 24, 2022, at 43 sites in 16 countries, 98% of the persons with infection were gay or bisexual men, 75% were White, and 41% had HIV; the median age was 38 years. Transmission was suspected to have occurred through sexual activity in 95% of the persons with infection.

Skin lesions were noted in 95% of individuals, with the most common anatomical sites being the anogenital area (73%); the trunk, arms, or legs (55%); the face (25%); and the palms and soles (10%). A wide spectrum of skin lesions was seen, including macular (flat), pustular, vesicular (blisters), and crusted lesions, and lesions in multiple phases were present simultaneously. The number of lesions varied widely, with most persons having fewer than 10 lesions and 10% having only a single genital ulcer (which can be confused for another sexually transmitted infection).

Mucosal lesions were reported in 41% of individuals, and among those with anorectal lesions, the involvement was associated pain, proctitis, tenesmus, or diarrhea (or a combination of these symptoms). Oropharyngeal symptoms were reported as the initial symptoms in 5% of the case series, with symptoms that included pharyngitis, odynophagia (pain when swallowing), epiglottitis, and oral or tonsillar lesions. Common systemic features included fever (in 62%), lethargy (41%), myalgia (31%), headache (27%), and lymphadenopathy (56%), symptoms that frequently preceded the rash. Of importance is that the clinical presentation was similar among persons with HIV infection and those without HIV infection.

Most individuals do not require treatment unless the lesions are very painful or disseminated (in multiple places). The main treatment available for disseminated monkeypox at this time (with multiple lesions) is tecovirimat (an oral antiviral which treats orthopoxviruses), which is available from the Centers for Disease Control and Prevention (CDC) and is getting easier to obtain.

As I've noted previously, a highly effective vaccine called Jynneos has been licensed in the United States to prevent monkeypox and smallpox. On June 1, the CDC updated its recommendations to say that Jynneos is the preferred postexposure prophylaxis for close contact of monkeypox cases (eg, household contacts or healthcare workers) and thereafter, many scientists, including myself, wrote about how we need to give Jynneos as a preventive vaccine to gay and bisexual men. The Jynneos vaccine is highly effective in protecting against monkeypox.

COVID-19 did not have an effective vaccine when it initially spread in the US in early 2020 and required masks, distancing, ventilation, testing, and contact tracing to try to minimize transmission. With monkeypox, we are not at that disadvantage. We have a vaccine and the US is finally procuring more doses. However, our current attempts to test and contact-trace our way out of this epidemic are failing, so we need to vaccinate those at risk (all sexually active MSM in the US).

Moreover, in terms of vaccine strategy, I think we need to be creative about spreading out the doses in this time of limited supplies. The usual dosing strategy for the monkeypox vaccine is one dose followed by a second dose 4 weeks later. I would advocate for the first-dose-first strategy that was used for the COVID vaccine in the UK, Canada, and India at the beginning of the vaccine rollout when supplies were limited. This means that we give one dose now to get as many doses out to MSM as possible followed by the second dose when vaccine supplies increase.

I also think we should hold off on vaccinating those who have had smallpox vaccination (which ended around 1970 in the US), since these individuals will likely still have some protection against monkeypox. Then, when vaccine supplies increase, we can extend doses to every MSM who wants to be vaccinated. Later, if we start to see significant rises in monkeypox infections in heterosexuals (which is not occurring now), the vaccine will be offered more widely to all sexually active individuals then.

Finally, I think the focus on the LGBTQ population is very helpful. Just like with HIV and COVID, it is important to define populations most at risk so we can prioritize targeted messaging and resources toward those groups. With HIV, it was counterproductive to say that all groups were at risk, and the same is true for monkeypox. If the infection spreads to all sexually active adults, the vaccine will eventually be offered to all of them (or simultaneously when HPV vaccine is offered to adolescents as a preventive vaccine for a new sexually transmitted infection).

Now that the monkeypox outbreak is officially recognized as a global health emergency, I will be providing you with regular updates. With this new vaccine we can hopefully get on top of this soon.

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About Dr Monica Gandhi
Monica Gandhi, MD, MPH, is an infectious diseases doctor, professor of medicine, and associate chief in the Division of HIV, Infectious Diseases, and Global Medicine at the University of California, San Francisco (UCSF). She is also director of the UCSF Center for AIDS Research (CFAR) and medical director of the HIV Clinic ("Ward 86") at San Francisco General Hospital. Her research focuses on HIV and women; adherence measurement in HIV treatment and prevention; and, most recently, on how to mitigate the COVID-19 pandemic.

Connect with her on Twitter: @MonicaGandhi9


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