Prognosis
Most cases are usually mild and self-limiting, and most patients will recover within 2-4 weeks without treatment.
Typically, more than 90% of survivors have no complications, regardless of vaccination status. In survivors who do develop long-term complications, the most common sequelae are disfiguring scarring of the skin (including pitted scars) and blindness.[1]
Persistent symptoms (e.g., anorectal or genital issues, fatigue, loss of physical fitness, pain, scarring, mental health issues) have been reported in up to two-thirds of patients 3-20 weeks after the initial infection in the 2022 global clade II mpox outbreak, which may significantly affect the patient's quality of life.[330]
The acute infectious illness results in immunity following recovery. Relapse of disease is rare, but is possible. One UK patient experienced a mild relapse 6 weeks after hospital discharge in 2019. The relapse was short, and was not associated with detectable viremia.[297]
The occurrence of a second febrile period when the lesions become pustular has been associated with deterioration of the patient’s general condition.[191]
Severe or complicated disease and death occurs more commonly in younger children and immunocompromised people.
Most reported deaths, prior to the 2022 global clade II mpox outbreak, occurred in younger children and immunocompromised people (e.g., poorly controlled HIV infection).[1]
In the early years of human infection, 100% of deaths were in children ages <10 years. However, between 2000 and 2019, children ages <10 years accounted for only 37.5% of deaths.[4]
No deaths have been reported in children and adolescents ages <18 years in the 2022 global clade II mpox outbreak.[45]
Patients with fatal disease had higher viral loads of the virus in their blood, maximum skin lesion count, and elevated transaminases.[1]
Severe complications and sequelae were more common among unvaccinated patients (74%) compared with vaccinated patients (40%).[191]
Adults ages >50 years appear to have a similar risk of hospitalization and death compared with adults ages <50 years, possibly due to older adults receiving the smallpox vaccine as part of their childhood immunization schedule.[331]
Case fatality rates (CFRs) vary according to virus clade, geographic location, and availability of medical facilities, and are vulnerable to case ascertainment bias during outbreaks.
Historically, the CFR of the clade Ia virus has been estimated to be 1% to 10%, while the CFR of the clade IIa virus has been estimated to be 1.4% to 3%.[1] The estimated pooled CFR was 8.7% for both clades in one systematic review (10.6% for clade Ia and 3.6% for clade IIa).[4] The overall CFR was 0% in an outbreak in the US in 2003.[59]
Fatalities due to the clade IIb virus are rare. Overall mortality has decreased in the 2022 global clade II mpox outbreak compared with previous outbreaks.[15] Approximately 1.2 deaths per 1000 cases have occurred globally during the outbreak, with 1.3 deaths per 1000 cases in the US.[332] The estimated pooled CFR varies by geographic location: 0.19% for the Americas, 0.33% for Europe, and 0% to 6% for Africa.[106] Causes of death have included multi-organ failure and encephalitis.[333][334] Whether mortality is associated with any specific factors is currently unknown. However, nearly all deaths in the US were in patients who were immunocompromised at the time of diagnosis.[332][335]
There is currently a lack of data on the CFR for the clade Ib variant. The reported CFR for clade Ib ranges from 0.3% to 1.4% in hospitalized settings, based on current data. This suggests that the CFR is much lower compared with clade Ia and similar to that of clade IIb.[36][63]
Globally, the overall CFR for both clades of mpox since 2022 is 0.2% (as of 30 March 2025), although most of the data comes from the 2022 global clade II mpox outbreak.[12]
Cases of suspected reinfection have been reported.
Reinfection is very rare, and has been reported in less than 0.001% of people in the US who previously had mpox.[166] Therefore, people who have recovered from mpox are not recommended to receive mpox vaccination.
Apparent cases of reinfection have been reported 3-6 months after recovery from initial infection, possibly with different strains of the virus.[336][337][338][339][340] Clinical features and outcomes of reinfection (after natural infection or vaccination) appear to be less clinically severe.[341]
Case definitions for mpox reinfection have been published by the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC).[90][202] See Criteria.
Further research is required on immunity after recovering from infection.
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