On 13 August 2024, the Africa Centres for Disease Control and Prevention (Africa CDC) declared a Public Health Emergency of Continental Security (PHECS). The next day, the WHO proclaimed another Public Health Emergency of International Concern (PHEIC)-the previous PHEIC, declared on 23 July 2022, having been lifted in May 2023. These pronouncements defined the official response to an outbreak of mpox-known as monkeypox until November 2022-which was first detected in eastern Democratic Republic of Congo (DRC) in November 2023, before spreading to the neighbouring countries of Burundi, Rwanda, Uganda, and Kenya. This outbreak has been attributed to sub-clade Ib of the mpox virus (MPXV), where the term clade refers to a grouping of organisms with a common ancestor. This new variant is more readily transmissible than clade IIb, which was responsible for the preceding outbreak of May 2022, and is also reported to cause more deaths.
Mpox was first identified in captive monkeys at the State Serum Institute in Copenhagen in 1958. The first human case was reported in a nine-month-old boy in north-western DRC, who was hospitalised in August 1970 with suspected smallpox. The first case outside Africa was reported from the American state of Wisconsin in 2003, in a three-year-old girl who was bitten by her pet prairie dog.
MPXV is an orthopox virus, as are the double-stranded DNA viruses that cause smallpox (variola), chickenpox (varicella), and cowpox (vaccinia). Several species of animals serve as natural hosts of MPXV, mostly rodents in the tropical rainforests of several central and west African countries. A mutated strain of clade I MPXV was reported from the gold-mining town of Kamitunga in South Kivu province, in eastern DRC, in early 2024. Sexual transmission involving truckers, miners, and sex workers was considered to be the major reason for the spread of the virus.
Most often, mpox is a mild and self-limiting illness. Symptoms may develop 10 to 14 days after infection, with a range of 6 to 21 days. Fever, chills, headache, sore throat, muscle ache, joint pain, backache, tiredness, and swollen lymph glands soon give way to a skin rash and mucosal ulcers (in the mouth, throat, rectum, urethra, and vagina). The skin rash spreads throughout the body and persists for up to two to four weeks. The skin lesions appear in crops, starting with flat macules, which progress through elevated solid papules, fluid-filled vesicles, to pus-filled pustules, in one-to two-day increments. Successive crops mean that these various stages of skin lesions may all be present at the same time. The pustules eventually burst, forming crusts. The patient is no longer infective once the crusts have fallen off and the lesions have healed, often with depigmented scars.
MPXV can spread from animals to humans (zoonotic infection) or between humans. Wild rodents (rats, mice, squirrels) or primates (monkeys) can infect humans through bites or scratches, contact with skin lesions or body fluids, or by the consumption of contaminated bush meat. Monkeys are not considered to be natural reservoirs of mpox infection, contrary to the initially assigned name for the illness. Human-to-human infection requires close contact, from sexual transmission, household transmission (shared bedsheets, towels), or droplet transmission (coughing or sneezing) consequent upon prolonged and intimate face-to-face interactions.
Real-time polymerase chain reaction (PCR) testing on skin swabs, discharges, or crusted lesions can detect MPXV DNA, thereby confirming the diagnosis. In the absence of skin lesions, throat swabs may help diagnose those with prodromal symptoms. The genetic clade can be identified by genomic sequencing of the detected virus.
The recent increase in number of cases of mpox may be related to waning population-level or so-called herd immunity to orthopoxviruses, following the withdrawal of smallpox vaccination after the global eradication of smallpox. Modified Vaccinia Ankara-Bavarian Nordic (MVA-BN), known as Jynneos in the US or Imvanex in Europe, is a live attenuated vaccinia virus, administered in two doses spaced 28 days apart, which can be used to immunise people against MPXV. Vaccination can either be initiated prior to exposure to the virus, to prevent infection, or within 14 days of exposure to lessen the severity of any ensuing illness.
Mpox sufferers should be isolated and their symptoms treated. Open skin lesions must be covered. The patient’s recent close contacts must be identified and tested. Most victims will nonetheless recover without specific treatment. Victims with compromised immunity may require vaccinia immune globulin (VIG) to provide temporary immunity against MPXV and tide them over the illness. The antiviral drug Tecovirimat, used to treat clade II infections, is, unfortunately, ineffective against clade Ib. Any treatments must be prescribed by professionals conversant with the most recent updates to clinical practice.
Reports of the detection of clade Ib MPXV in Sweden on 15 August, in a recent visitor to the DRC, has increased public anxiety, this being the first case to be diagnosed outside the African continent. A media frenzy of reports, a proliferation of amateur virologists, and a profusion of statements by healthcare professionals all have the potential to confuse and alarm. In these circumstances, it is important to be guided by public health agencies and not to rely upon social media and sundry self-appointed experts as the primary sources of information.
Ashis Banerjee