Mpox: Often Mild, Although Potential for Complex Morbidity Exists

Data from a retrospective study published in The Lancet Infectious Diseases suggested that although mpox (monkeypox) infection is often mild, severe disease and complex comorbidity can occur among immunocompromised patients. However, the study authors further report that no deaths were attributed to mpox among their study participants hospitalized during the outbreak in the summer of 2022.

Investigators sourced data collected between May and August 2022 from 16 hospitals in England. All patients (N=156) who were admitted with signs and symptoms consistent with mpox were evaluated for infection by polymerase chain reaction (PCR), and trends in treatments and outcomes were reviewed.

The median age of the study population was 35 (interquartile range [IQR], 30-44) years, 98% were men, 90% identified as homosexual or bisexual men, 67% were White, 30% were HIV-positive, and 6% were immunosuppressed.

Patients were diagnosed with mpox at a median of 6 days after symptom onset and admitted to the hospital 7 days after symptom onset.

Compared with skin lesions, mpox cycle threshold (Ct) levels were significantly higher in urine, blood, and throat samples (all P <.0001).

At presentation, the most common symptoms included severe pain (57%), severe rectal or perianal pain (28%), genital cellulitis (10%), and upper respiratory tract disease affecting swallowing or breathing (10%). In addition, most patients (58%) had a secondary infection at admission, including gonorrhea (13%), chlamydia (10%), and herpes simplex virus (10%).

Patients with a secondary infection were more likely to report fever symptoms (79% vs 59%) or lymphadenopathy (79% vs 50%). They also had higher peak hemoglobin (median, 151 vs 145 g/L), white blood cells (median, 10.2 vs 8.7×10⁹ cells/L), C-reactive protein (median, 66 vs 41 mg/L), alanine transaminase (median, 55 vs 35 IU/L), and alkaline phosphatase (median, 89 vs 84 IU/L) levels and lower peak creatinine (median, 85 vs 88 mmol/L) levels compared with those without secondary infection, respectively.

Patients with a secondary infection had a higher rate of antibiotic treatment (99% vs 51%), tecovirimat treatment (28% vs 20%), and surgical procedures (11% vs 1%) as well as a longer duration of hospitalization (median, 7 vs 4 days) compared with those without secondary infection, respectively.

For the cohort of patients who received tecovirimat (n=38), treatment initiation occurred at a median of 11 days after symptom onset, and rectal or perianal pain (18%) was the most frequently reported indication for treatment. Additional indications included ocular or periocular disease (16%), upper respiratory tract involvement (16%), and urologic symptoms (16%), among others.

Patients who received tecovirimat were more likely to be HIV-positive (42% vs 26%) and severely immunocompromised (13% vs 4%), and to have impaired liver function (45% vs 31%) compared with patients who did not receive tecovirimat, respectively.

No deaths occurred among participants enrolled in the study.

A limitation of this study is that its findings may not be representative of the entire UK population. These data were sourced from hospitals that are believed to represent more than 90% of mpox diagnoses; however, the absolute number of hospitalizations for mpox infection in the UK is not known.

These data indicate that although life-threatening infection is rare among patients with mpox, immunocompromised patients may be at risk for severe disease and complications, including superimposed bacterial infection. Multidisciplinary inpatient management is advised to improve outcomes for this population. The study authors comment, “We believe our specialist clinical network approach helped optimize inpatient care and knowledge-sharing for this emerging infectious disease in the UK.”