Credit: Ministry of Health (sante.lu)

Monkeypox, a zoonotic disease, i.e. transmitted from animals-to-humans, is endemic in countries of central and west Africa and was first detected in humans in the Democratic Republic of the Congo in 1970.

The virus had been first detected when a pox-like disease occurred in monkeys in a laboratory in Denmark in 1958, and hence the name: monkeypox.

Outside Africa, first outbreak in humans was reported in the United States in 2003 with a total of 81 human monkeypox cases after close contact with pet mammals, predominantly rodents. No human-to-human transmission was identified and most cases could be tracked to importation of small mammals from Ghana to Texas. More recently, in May 2022, a multi-country global outbreak has been reported, including human-to-human transmission.

According to the European Centre for Disease Prevention and Control (ECDC), as of 25 May 2022, a total of 219 cases have been identified in non-endemic countries, including 118 cases in the European Union (EU). Luxembourg's Ministry of Health confirmed no known cases of monkeypox across the Grand Duchy as of 25 May 2022.

In addition, the World Health Organization (WHO) reported over 1,300 suspected and confirmed cases of monkeypox in Africa between 1 January and 1 May 2022, with the majority of them in the Democratic Republic of the Congo (1,238), a central African nation with an estimated population of 108 million.

Origins

Following the smallpox eradication declared worldwide in 1980 and subsequent cessation of smallpox vaccination, monkeypox, similar to the smallpox class of orthopoxviruses, has been generally reported in rural areas in proximity to tropical rainforests and, more recently, in urban areas in Africa.

The twelve monkeypox endemic African countries are: Benin, Cameroon, the Central African Republic, the Democratic Republic of the Congo, Gabon, Ghana, Ivory Coast, Liberia, Nigeria, the Republic of the Congo, Sierra Leone and South Sudan.

Natural Hosts

The Monkeypox virus in central and west Africa has been detected in many animals including squirrels, rats, doormice, striped mice and different species of monkeys, amongst others. Whilst a natural reservoir of monkeypox virus has not yet been determined, rodents are suspected as the most likely.

Symptoms

Monkeypox symptoms typically include fever (above 38.5 degrees C), headache, backache, fatigue, swollen lymph nodes and localised or generalised maculopapular or vesiculopustular rashes.

The time between infection to the onset of symptoms is typically between one to two weeks while symptoms last between two and four weeks.

Severity

Monkeypox symptoms are similar but less severe to smallpox, while secondary infections may include encephalitis, secondary skin bacterial infections, dehydration, conjunctivitis, keratitis and pneumonia. Case fatality ratio of around 3% to 6% is generally accepted.

WHO reported 57 deaths related to monkeypox in the Democratic Republic of the Congo between 1 January and 1 May 2022, with an estimated case fatality rate of 4.6% (1,238) while, in the same period in 2021, with 41 deaths, the case fatality rate stood at 3.0% (1,376 cases).

According to ECDC, while current outbreak have mild disease symptoms, monkeypox infection may cause severe disease in young children, pregnant women and immunosuppressed people.

Transmission

Eating uncooked (raw) or undercooked infected animals is a possible risk factor, while direct transmission can occur from a bite or direct contact with an infected animal's blood, meat, bodily fluids, or cutaneous or mucosal lesions. Human-to-human transmission, similar to smallpox, can occur through direct contact of lesions or body fluids of an infected person, or during a prolonged close contact via respiratory droplets or sharing of contaminated objects. Other transmission routes, such as mother-to-child transmission during birth or during hospital or other health care facility stay are possible but extremely rare.

Notably, most cases in the current outbreak in non-endemic countries were detected in young homosexual men. According to ECDC, most cases presented with lesions on the genitalia or peri-genital area, indicating that transmission likely occurred during close physical contact during sexual activities. Moreover, these are also the first cases worldwide reported among homosexual men.

However, WHO has reminded that stigmatising people because of a disease is never okay and anyone can get or pass on monkeypox, regardless of their sexuality.

Detection

Laboratory-confirmed detection is possible through monkeypox virus specific PCR assay and/or DNA sequencing methods. Serology, antigen and antibody detection methods do not provide monkeypox-specific confirmation.

Vaccine

There is no specifically-licensed vaccine against monkeypox in the EU.

A third-generation smallpox vaccine, Modified Vaccinia Ankara - Bavarian Nordic (MVA-BV / Imvanex) was authorised by the European Medicines Agency (EMA) in 2013 for use against smallpox under exceptional circumstances and, according to ECDC's risk assessment report on 23 May 2022, EMA is needed to clarify the authorisation status of the MVA-BV vaccine against monkeypox in the EU. ECDC also noted that the lack of efficacy data for MVA-BV vaccine against monkeypox in humans as well as safety data for in immunocompromised persons.

However, following the detection of two monkeypox cases in the United Kingdom in 2018, MVA-BV was employed for "off-label use".

Tecovirimat, also known as TPOXX, is an antiviral medication for smallpox treatment approved by the United States Food and Drug Administration (FDA), but the Centers for Disease Control and Prevention (CDC) holds an Expanded Access Investigational New Drug Protocol (EA-IND) that allows its use in case of monkeypox outbreak. However, data is not available on the effectiveness of Tecovirimat in treating human cases of monkeypox.

Observational studies in 1980s showed that smallpox vaccine is up to 85% effective in preventing monkeypox infection and prior smallpox vaccination may result in milder monkeypox illness.

WHO recommends national health authorities to consider offering smallpox vaccine to healthcare workers and those treating monkeypox patients or are contact with monkeypox samples or specimens.

It should be noted that the smallpox vaccine is currently not available to the general public.

Prevention

On Saturday 21 May 2022, Luxembourg's Ministry of Health recommended that any suspected case and anyone with symptoms indicative of monkeypox should consult the national infectious diseases unit of the Centre Hospitalier de Luxembourg (CHL) and refrain from sexual activity or any other type of activity involving close contact until monkeypox has been ruled out or the infection has been resolved.

On Monday 23 May 2022, WHO confirmed that the current outbreak does not require mass vaccinations, rather hygiene and safe sexual behaviour will help control the spread.

ECDC recommended suspected or confirmed monkeypox cases to remain isolated until their rash heals completely and avoid close physical contacts with people and pets.