Mpox: Testing, diagnosis and clinical management

To date, most cases have occurred in MSM, but there have also been reports overseas of women and children acquiring the infection. The mean incubation period from the time of exposure to the first symptom appearing is 7 days, with 95% of individuals developing symptoms within 17 days.

Figure 2. Umbilicated mpox vesicle on male’s cheek at day 4 of infection.

Initial symptoms include a flu-like illness with fever, malaise, headache and fatigue. This is often accompanied by lymphadenopathy. Shortly after the prodrome, a rash appears with lesions starting as macules and progressing to raised papules and vesicles (see Figures 1 & 2). The vesicles may fill with pus, ulcerate, then scab and fall off. The rash is typically distributed on the face, extremities and genitals. MSM may experience symptoms that include anorectal pain, proctitis with bleeding, penal oedema with balanitis and phimosis. Sore throat, odynophagia, epiglottitis and tonsillitis may also occur. The most common location of lesions reported in MSM were the anogenital area (73%), trunk and extremities (55%), face (25%) and palms and soles (10%). Most cases had fewer than 10 lesions, and some had only a single genital lesion.

Complications can occur in immunosuppressed individuals, pregnant women and young children. These include pneumonia, encephalitis and eye infections. Hospitalisation is uncommon and mortality rare, but at least four people in nonendemic countries have died. People should remain in isolation for the duration of the illness, which usually lasts 2 to 4 weeks. The disease is notifiable in Australia.

"If clinically indicated, testing for other likely pathogens should also be performed including herpes simplex, varicella zoster or bacterial infection."

Like many viruses, mpox cannot be diagnosed by symptoms alone. The symptoms closely resemble those of other rash-producing illnesses such as chickenpox, zoster, measles, syphilis, scabies, bacterial skin infections and allergic reactions. Laboratory testing is, therefore, essential for an accurate diagnosis.

For most patients, management is symptomatic, including pain relief. Treatment with antivirals is recommended for people with severe disease or who are at high risk of severe disease.

Vaccination is available in Australia for high-risk groups from the Department of Health. The JYNNEOS vaccine is FDA approved for smallpox and mpox. It uses live attenuated vaccinia virus that is incapable of replicating. It is administered as a two-dose series, with peak antibody response occurring 2 weeks after the second dose. It is thought to be 85% effective at preventing mpox. The vaccine can be administered as post-exposure prophylaxis. When administered up to 4 days after exposure, vaccination can prevent disease onset altogether, but even receipt of vaccine up to 2 weeks after exposure can reduce symptom severity.

The risk of transmission of mpox in the healthcare setting is low if appropriate personal protective equipment is worn. Healthcare workers should wear a gown, gloves, eye protection and an N95 mask. A person with suspected or confirmed mpox infection should be masked immediately, have lesions covered and be placed in a single-person room.

A person with mpox infection should avoid close contact with others until the lesions are completely healed. This can take several weeks. It is unknown whether recovery from mpox protects against subsequent infection.