Hygiene and disinfection measures
for infections with the monkeypox virus (as at 25.07.2022)

Updated notification as of July 25, 2022

Priv.-Doz. Dr. Maren Eggers (VAH, GfV, DVV)[1]Prof. em. Dr. med. Martin Exner (VAH, DGKH), Dr. Jürgen Gebel (VAH),
Carola Ilschner (VAH), Prof. Dr. Holger F. Rabenau (GfV, DVV), Dr. Ingeborg Schwebke (GfV, DVV)

1 Introduction

Monkeypox is a zoonotic viral disease caused by an infection with the monkeypox virus. This is an enveloped double-stranded DNA virus and belongs to the genus of orthopoxviruses of the Poxviridae family. The genus of orthopoxviruses also includes variola virus (the causative agent of smallpox), vaccinia virus, horsepox virus and cowpox virus.

At the end of the 18th century, the English doctor Edward Jenner used cowpox lymph (vaccina, derived from vacca, the cow) as a vaccine for the first time. The process known as "vaccination" quickly became established. In addition to the variolation of cows or human-to-human vaccination, other animals such as rabbits, pigs, sheep, donkeys, horses and goats were also used as intermediate hosts to improve the effectiveness of the lymph. In fact, vaccines derived from cowpox or horsepox were used interchangeably for smallpox vaccination in the 19th century [1]. The vaccinia virus, whose origin is not entirely clear due to the different intermediate hosts and of which there are four standardized variants, is still used today in a modified form for protection against smallpox (variola virus, monkeypox virus) and in research, e.g. as a test virus for testing the efficacy of disinfectants [2].

Monkeypox was first discovered in 1958 when two outbreaks of a smallpox-like disease occurred in (macaque) monkey colonies kept for research purposes. This is where the name "monkeypox" comes from. The natural reservoir of monkeypox viruses is still unknown, but they have a broad host range. Antibodies against monkeypox have been detected in various rodent species (red squirrels, sun squirrels, Gambian giant hamster rats and other mouse and rat species), but also in mangabeys, guenons and marmosets [3]. The first case of monkeypox in humans was detected in the Democratic Republic of Congo (DRC) in 1970, when efforts to eradicate smallpox were intensified. Since then, monkeypox in humans has been described in several other Central and West African countries: Cameroon, Central African Republic, Côte d'Ivoire, DRC, Gabon, Liberia, Nigeria, Republic of Congo and Sierra Leone [3, 4]. An increase in cases has been observed since 2017 [5].

Based on sequence analyses of monkeypox virus isolates, these have so far been divided into two clades (variants): the West African and the Central African viruses. The latter occur mainly in the Congo Basin. Compared to the West African virus strains, which generally cause milder infections, they lead to infections with higher lethality (case fatality rate (CFR)%, i.e. the proportion of fatal courses of a disease: approx. 11 vs. 1 %), more severe courses of disease and higher reproduction figures (R0: 0.8 vs. 0.3); these data come from Africa, mostly children are affected [3].

Outside of Africa, cases of monkeypox in humans have rarely occurred in connection with international travel or animal imports. In 2003, the first major monkeypox outbreak occurred in the USA through transmission of the virus from infected prairie dogs. The prairie dogs had been infected by animals imported from Gambia and housed in an enclosure with them. Transmission to humans occurred via both invasive (bites, scratches) and non-invasive contacts (e.g. touching, feeding) [6]. Individual travel-associated case reports have been reported e.g. from Singapore [7] as well as from the USA, Israel and the UK [8, 9].

2 Epidemiology of the current outbreak

Since May 6, 2022, 15,734 travel-independent confirmed cases have been reported worldwide (source: Global Health Mapbox, https://map.monkeypox.global.health/country, as of July 22, 2022). This outbreak cluster of 2022 belongs to a new clade 3 identified by genome sequencing, which also includes clade 2 of the West African variant [10].

Nach Angaben der Pan American Health Organizsation wurden zwischen dem 1. Januar und dem 7. Juli 2022 insgesamt 7892 bestätigte Fälle gemeldet (aus 63 Mitgliedstaaten in 5 Regionen der Regionen der WHO), einschließlich 3 Todesfälle (aus Nigeria und der Zentralafrikanischen Republik). Bis zum 7. Juli 2022 wurden 82% (6496 Fälle in 34 Ländern) der bestätigten Fälle in der Europäischen Region der WHO gemeldet; 15% (1184 Fälle in 14 Ländern) in der Amerikanischen Region der WHO; 2% (173 Fälle in 8 Ländern) in der Afrikanischen Region der WHO; 1% (24 Fälle in 4 Ländern) in der der WHO-Region Westpazifik und <1% (15 Fälle in 3 Ländern) in der der Östlichen Mittelmeerregion der WHO. In den letzten 7 Tagen [2. bis 9.7.2022] gab es einen Anstieg der weltweit gemeldeten Fälle um 41,6%. Im gleichen Zeitraum gab es einen Anstieg von 82% in der Region Afrika, 57% in der Region Nord- und Südamerika und 38 % in der Region Europa. Es handelt sich also um ein sehr dynamisches Geschehen. Weltweit sind 78 % der bestätigten Fälle Männer im Alter von 18 bis 44 Jahren. Insgesamt wurden
98 % der Fälle als Männer identifiziert, die Sex mit Männern haben (MSM), und von diesen sind 41 % HIV-positiv. Von den Fällen gaben 47 % an, dass sie zuvor bei sozialen Ereignissen mit sexuellem Kontakt mit der Krankheit in Berührung gekommen sind. Von den 1.110 Fällen, zu denen Informationen vorliegen, sind 113 Beschäftigte im Gesundheitswesen. Ob die Infektion in diesen Fällen durch berufliche Exposition verursacht wurde, wird derzeit untersucht [11].

In Germany, cases have been reported from all federal states [12, 13]; the obligation to report confirmed cases in accordance with Sections 6 and 7 of the Infection Protection Act (IfSG) applies (2,352 cases as of 25.7.2022). Even though the WHO declared the outbreak a "public health emergency of international concern" on 23.7.2022 due to its dynamic nature, the Robert Koch Institute (as of 25.7.2022) still considers the risk to the general population to be low [12].

The WHO has set up an Emergency Committee and is publishing recommendations for action to protect public health. It has also reported cases of infected children in the UK, Spain and France with mild cases [14].

3 Clinical picture

Monkeypox is a rare but potentially serious viral disease that typically begins after an incubation period of 5-21 days with a flu-like illness (initially with fever (> 38.3 °C), headache, muscle aches and fatigue) and swelling of the lymph nodes (cervical, inguinal) and develops into a rash on the face and body.

The eruptive stage begins with typical enanthema (oropharynx) and exanthema on the face, hands and forearms with centripetal spread over the body with subsequent development of redness and uniform stages of efflorescence typical of smallpox (macules, vesicles, pustules and crusts). This occurs in approx. 80 % of patients within a few days - in 20 % of patients a polymorphic exanthema occurs - similar to varicella. The lesions heal after drying out and desquamation (sometimes with scarring). It was previously assumed that the infectiousness lasts from the beginning of the prodromal stage at least until the crust of the skin lesions falls off [15].

People who have been vaccinated against smallpox generally develop fewer efflorescences than those who have not been vaccinated. In addition, non-vaccinated people often develop ulcerations on the mucous membranes of the oral cavity with pharyngitis and tonsillitis, conjunctivitis with eyelid oedema and very painful lesions in the genital area. Rarely, blindness and disfiguring scars occur as permanent damage. Severe, fatal hemorrhagic forms are rare, sometimes mild forms with less than 10 pockmarks and subclinical infections are observed.

Overall, the prognosis is favorable. In the past, a higher probability of severe disease and mortality was only observed in children under 8 years of age [16, 17].

3.1 Clinical picture: Special features of the monkeypox outbreak in 2022 (clade 3)

Current reports show that the symptoms of the clade 3 monkeypox diseases now prevalent in Europe differ from earlier descriptions. Symptoms of the prodromal stage are often absent. The skin lesions first appear in the urogenital and anal regions and not on the hands and soles of the feet, as is usually the case. The lesions were also often at different stages and may have appeared before systemic symptoms. The team of authors of a study published in Lancet Infectious Diseases in July 2022 therefore propose an adjustment to the case definition [18].

Asymptomatic cases are also reported in a preprint study from Belgium. Anorectal swabs showed a positive result in three (1.3%) of 224 MSM who were retrospectively tested for monkeypox. All those affected stated that they had not had any symptoms [19].

The possibility of generalized and severe courses in cases of reduced immunity (e.g. infants and young children, patients with immunosuppressive treatment, patients with chronic immunodeficiency, elderly people, pregnant women) should be taken into account. It is therefore also important to protect these population groups in particular.

For information on vaccination status, it is advisable to record the vaccination status from the vaccination record. A Eurosurveillance study found that a positive vaccination status against smallpox viruses was also reported by patients under 40 [20].

4 Transmission paths

The monkeypox virus can be transmitted via various routes, from animal-to-animal (mainly various rodent species), from animal-to-human and from human-to-human. In addition, the possibility of human-to-animal transmission cannot be ruled out in the event of contact with high viral loads. Both monkeys and humans are poor hosts for the monkeypox virus [21].

4.1 Human-to-human transmission

In human-to-human transmission in the current outbreak, direct transmission via close contact with infectious skin lesions (e.g. via burst blisters) is in the foreground. The blisters and pustules contain high viral loads. Entry points are small skin lesions as well as the mucous membranes and the respiratory tract.

Indirect transmission via infectious material (e.g. via bed linen [skin/scab particles], towels, clothing, hand contact surfaces) is also possible. Vertical transmission from mother to child has also been described in rare cases [22, 23]. Transmission via larger respiratory droplets after prolonged personal contact appears to play a rather minor role in this outbreak, but may be relevant for prevention measures in the context of major events.

In a Hamburg hospital, a systematic examination of the viral load on selected surfaces of two patient rooms with anterooms was carried out on the 4th day of hospitalization of monkeypox patients. Using PCR analysis, it was found that the surfaces close to the patients in the wet rooms (water tap, soap dispenser lever, toilet seat) had a particularly high viral load, as did the seat surfaces of chairs and the display of patients' cell phones as well as textiles (pillows, clothing around the anal area) used by the patients. Furthermore, surfaces that were presumably touched by medical staff and thus contaminated, such as cupboard handles and door handles in the anteroom, showed high viral loads. The authors point out that these are primarily the results of a PCR analysis, i.e. viral DNA, and not the cultivation of infectious monkeypox viruses. Interestingly, however, they were able to cultivate the monkeypox virus in three of the samples collected from one patient, namely from the examiner's glove, the operating lever of the soap dispenser and a towel on the patient's bed. All three samples had more than¹⁰⁶ copies per sample (^{>103 cp/cm2}) [24].

The transmission of monkeypox virus via semen, urine, stool, blood and tear fluid has also not yet been conclusively clarified, although positive PCR test results were found in some of these materials in a recent study [17]. The evidence is reinforced by an even more recent Spanish study from Barcelona, which shows how frequently the virus is found not only in skin lesions, but also in the throat, urine and semen. The Robert Koch Institute succeeded in cultivating viruses capable of replication from ejaculate [25]. PCR-positive results were also obtained in stool [26].

The question of airborne transmission or drift has also not yet been clarified. Therefore, windows should only be ventilated when the door is closed (no cross ventilation).

The longest chains of infection that have been observed so far involved six to nine people [27].

5 Properties of monkeypox

Studies with the vaccinia virus - related to the monkeypox virus - showed that this virus can remain infectious on surfaces for up to 56 days [28]. Stability on textile fibers was also investigated with the vaccinia virus. According to these studies, the virus could still be cultivated from wool fabric after up to four weeks and from cotton after four to eight days; textiles contaminated with virus-containing dust even remained infectious for up to twelve weeks [29, 30]. In the publication by Adler et al., there are indications that the virus could be detected in the throat swab of some patients for up to three weeks (in one case from 2018 even up to 41 days) after diagnosis using a PCR test [17]. Whether this was just "residual nucleic acid" or infectious virus was not investigated.

The period during which a person infected with monkeypox is infectious is currently estimated to be up to 4 weeks. The infectious dose of the monkeypox virus is not known. In non-human primates, the infection could be triggered by the intrabronchial administration of ^5×104 plaque-forming units (PFU), i.e. approx. 50,000 viruses [31].

According to current knowledge, the environmental stability is comparable to that of the vaccinia virus. Monkeypox viruses are highly resistant to desiccation and can survive for months to years in the crusts of skin lesions [32].

6 Preventive measures

6.1 Vaccination

In 1980, human smallpox was declared eradicated worldwide and vaccination against smallpox was discontinued in 1976 in what was then West Germany and 1982 in East Germany. Subsequently, the monkeypox virus spread as the most important smallpox virus for public health - alongside cowpox (which was transmitted, for example, via "cuddly rats" kept as pets) [33, 34, 35].

The smallpox vaccine Imvanex against smallpox, which contains a modified form of the Ankara vaccinia virus (MVA) that is no longer able to replicate, has been approved in the EU. In the USA and Canada, the approval of this vaccine also extends to vaccination against monkeypox. The European Medicines Agency (EMA) has now also approved this extension of the indication for Imvanex [36]. According to the recommendation of the Standing Committee on Vaccination (STIKO) of June 21, 2022, vaccination with Imvanex (MVA-BN) is currently recommended under certain conditions for post-exposure prophylaxis after monkeypox exposure of asymptomatic persons and as an indication vaccination of persons with an increased risk of exposure and infection [37].

In the meantime, the vaccine is available in practices in Germany and vaccinations in accordance with STIKO recommendations have begun. The organization and vaccination is regulated by the federal states.

6.2 Hygiene measures

The most important non-pharmaceutical preventive measure to prevent the spread of monkeypox and disease is to avoid close contact with an infected person. Patients and people living in the same household as a monkeypox patient should receive medical advice and, if possible, training on what hygiene measures to take and how to carry them out properly.

6.2.1 Disinfection

Smallpox viruses are enveloped viruses that can be inactivated by disinfectants with limited virucidal efficacy. As against SARS-CoV-2, disinfectants with proven "limited virucidal" efficacy are generally suitable for disinfection. In comparative studies with various enveloped viruses (e.g. hepatitis C virus, Ebola virus, influenza virus, coronavirus), vaccinia virus proved to be the most resistant virus [38-43]. The environmental stability of vaccinia viruses and monkeypox viruses is comparable [44, 45].

Products with the "limited virucidal PLUS" and "virucidal" efficacy ranges can also be used. The disinfectant list of the VAH or the disinfectant list of the Robert Koch Institute are available for selecting products.

With regard to the problem of the stability of the virus, e.g. in skin flakes and crusts, it is important to ensure that the efficacy test for surface disinfectants under high organic load has been carried out in accordance with the applicable test standards in the practical test in accordance with the requirements and methods for VAH certification of chemical disinfection procedures Annex V (as of November 1, 2021 Chapter V2A [46]). Surfaces close to the patient that are visibly contaminated with skin exfoliation and skin crusts should be removed in advance with a disposable disinfectant wipe, which is then immediately disposed of with the residual waste. Disposable gloves must be worn during all cleaning and disinfection measures and hands must be disinfected after use.

The use of disinfectants with the "limited virucidal PLUS" or "virucidal" mode of action should only be discussed (e.g. for surface disinfection) if they could penetrate crusts/scabs due to their mode of action and inactivate the virus inside, if prior efficient cleaning of the surfaces is not possible.

Laundry disinfectants are an exception in this respect, as the European standardization and also the VAH and RKI lists only have a virucidal effect.

If no VAH certificate is available, it is recommended that the test reports and expert opinions submitted by the manufacturer be evaluated by independent experts [47, 48].

The criterion for selecting a disinfectant should not be a specific active ingredient or group of active ingredients, but the manufacturer-independent proof of efficacy for the required spectrum of activity for a specific product.

The importance of laundry preparation, including the preparation of wiping utensils, for example for floor cleaning (mops), should be emphasized. Care must be taken to ensure that bed linen and underwear are collected in such a way that there is as little environmental contamination with skin crusts as possible, as the viruses embedded in these are much more difficult for the disinfectant to reach. In clinical and nursing environments, chemothermal reprocessing with a virus-effective, VAH- or RKI-listed process is required for laundry reprocessing [49].

Table 1: Hygiene measures and disinfection for households in which infected people live.

Table 2: Hygiene measures and disinfection in the medical environment.

Further information on case definition, management of contact persons, hygiene measures in patient care, at major events and in households with infected patients has also been published by the Robert Koch Institute (partly together with the BZgA)(www.rki.de/affenpocken).

7 Conclusion

Disinfectants against monkeypox must have at least proven efficacy against enveloped viruses ("limited virucidal"); products with the "limited virucidal PLUS" and "virucidal" efficacy ranges can also be used. The disinfectant list of the VAH or the disinfectant list of the Robert Koch Institute are available for selecting products. Particularly in the case of contamination with crust or scab material, it should be noted that the protein load can have a protective or stabilizing effect on monkeypox. Therefore, cleaning should always be carried out before disinfection. Preventive measures such as vaccination and hygiene must be taken in the vicinity of people suffering from monkeypox to prevent transmission to small children, pregnant women or people with a pronounced immunodeficiency.

Prof. em. Dr. med. Martin Exner, University Hospital Bonn, Dr. Jürgen Gebel (VAH), University Hospital Bonn, Carola Ilschner (VAH), University Hospital Bonn, Prof. Dr. Holger F. Rabenau, University Hospital Frankfurt, Dr. Ingeborg Schwebke, Berlin

Citation reference:

Eggers M, Exner M, Gebel J, Ilschner C, Rabenau HF, Schwebke I. Joint communication from VAH and the Virus Disinfection Commission of DVV and GfV: Efficacy of disinfectants against monkeypox viruses. Status 25.7.2022. HygMed 2022 (7/8): in print. Available at www.vah-online.de and https://g-f-v.org/komissionen/

*Joint communication from VAH and the Virus Disinfection Commission of DVV and GfV as of 27.5.2022, published online: https://vah-online.de/files/download/news/20220527_Mitteilung_Affenpocken_VAH_DVV_GfV_final.pdf

[1] Corresponding author

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