Mpox (formerly known as monkeypox) is a DNA virus of the Orthopoxvirus genus, the same genus as smallpox. It was first isolated in monkeys in 1958; the first human case was identified in the Democratic Republic of the Congo (previously Zaire) in 1970.¹ This article provides a summary and review of the best available patient-oriented evidence for mpox. Additional information about mpox is available from the American Academy of Family Physicians.²

Epidemiology

• In addition to monkeys and apes, dogs, hedgehogs, and some rodent species (including squirrels and prairie dogs) can be infected with mpox.³

• Before 2022, most cases of mpox occurred in the Democratic Republic of the Congo.⁴ The first reported cases of mpox outside Africa occurred in the Midwest United States in 2003.^4,5 The outbreak was traced back to prairie dog pets that were infected by exotic animals imported from Ghana.^4,5

• Starting in 2022, increasing numbers of cases of mpox have been reported outside the African continent. A case series of 528 infections diagnosed between April 27 and June 24, 2022, and involving 16 countries found that 98% of people infected were gay or bisexual men and that 41% of those infected were coinfected with HIV. Among those infected, 29% had a concomitant sexually transmitted infection. Hospitalization was required for 70 patients (13%) for pain control, soft tissue superinfection, pharyngitis, and infection control. No deaths were reported.⁶

• As of June 7, 2023, a total of 30,468 cases of mpox had been confirmed in the United States.⁷ World Health Organization data indicate a global total of 87,929 cases, with 146 deaths as of June 6, 2023.⁸

Prevention

• Transmission is primarily through contact with skin lesions. Skin-to-skin contact should be avoided with those suspected to have mpox. Gloves should be used when managing the laundry of people thought to be infected.^9,10

• In addition to skin lesions, the virus has also been detected in samples taken from the anus, throat, blood, urine, and semen of individuals infected with mpox.¹¹

• For health care workers caring for patients with suspected mpox, wearing personal protective equipment with gown and gloves is recommended to prevent transmission. Because risk of spread by the respiratory route can occur, eye protection and N95 respirators are also recommended.^9,12

• In the hospital, patients do not necessarily need a negative pressure room. Patients should have their own room with a private bathroom. Lesions should be covered with protective clothing or gauze when possible.⁹

• Individuals should avoid sex (anal, oral, or vaginal) and intimate contact with people who have mpox.¹³ Individuals can reduce their risk of being exposed to mpox by limiting the number of sex partners, avoiding sex clubs and sex parties, and limiting intimate contact in high-risk settings. Use of condoms and gloves may help prevent transmission, as can other barriers to skin-to-skin contact.¹³

• Those recovered from mpox and their sex partners should use barrier protection during intercourse for at least 12 weeks after resolution of symptoms to prevent spread to others.¹⁴

• A survey from the Centers for Disease Control and Prevention (CDC) shows that communication about the monkeypox virus leads to changes in sexual behaviors among men who have sex with men.¹⁵

VACCINATION

• Two vaccines are currently licensed by the U.S. Food and Drug Administration (FDA) for use against mpox.

• Jynneos (smallpox and mpox vaccine, live, non-replicating) is a live, attenuated vaccine that is safe for immunocompromised patients and comprises two doses, four weeks apart. Incidence of mpox was 14 times higher in those who were unvaccinated compared with those who received at least one dose of the Jynneos vaccine.^16,17 Redness, swelling, and pain at the site of the injection are common. In trials, serious adverse events occurred at a rate of 1.5% in those given Jynneos compared with 1.1% in the placebo group among patients who were vaccinia vaccine naive.¹⁸ Acute cardiac adverse events of special interest occurred in 1.3% of those given Jynneos compared with 0.2% in those given placebo.¹⁸ Events included asymptomatic troponin I elevation, electrocardiogram abnormalities, and palpitations; none were considered serious.¹⁸ A 0.5-mL dose of Jynneos is given subcutaneously to patients younger than 18 years, whereas those 18 years and older may be given a smaller 0.1-mL dose intradermally, according to CDC guidance.^19,20

• ACAM2000 (smallpox [vaccinia] vaccine, live) is a live vaccinia virus vaccine that should be given only to immunocompetent, nonpregnant people and should be avoided in those with skin conditions such as atopic dermatitis. It should not be used in people who have HIV or AIDS.²¹ This vaccine comprises one percutaneous dose via a multiple puncture technique with a bifurcated needle.

• It is possible to transmit the ACAM2000 vaccine to close contacts. Precautions should be taken to avoid accidental inoculation (e.g., covering the vaccination site and the lesion that the vaccination produces with a gauze bandage and washing hands with soap and water or using an alcohol-based hand sanitizer after contact with the site or after covering with bandaging, clothing, or linens (e.g., sheets, pillowcases, towels). ACAM2000 carries an FDA boxed warning for possible myocarditis and pericarditis (5.7 per 1,000 vaccinees; 95% CI, 1.9 to 13.3), and rare instances of encephalitis (1.4 to 24.7 per million) and generalized vaccinia (58.9 to 74.2 per million in the 2002 to 2005 administration of a previous iteration of live vaccinia vaccine) have occurred.²² ACAM2000 may be used in patients one year or older.²¹