Monkeypox Virus: How Likely is a Local Outbreak?

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INFECTIOUS DISEASE

Medical writer: Christy Leung | Last updated: 30 May 2022 | In: Infectious Disease

Article Keywords

orthopoxvirus, tecovirimat, vaccination, monkeypox, smallpox

Just two years after Coronavirus Disease 2019 (COVID-19) emerged, global communities are now concerned about a recent monkeypox outbreak. Monkeypox is a virus which, like smallpox, belongs to the Orthopoxvirus genus.¹ Wild animals, such as monkeys and rodents, are its reservoirs; humans can acquire the virus by direct contact with infected animals, respiratory droplets, or body fluid transmission.² Monkeypox is diagnosed by obtaining skin lesion scrapings for electron microscope visualisation and lesion fluid for viral PCR.³ It has an incubation period of less than two weeks⁴, then presents with systemic signs (fever, chills, sweats), lymphadenopathy, and characteristically sequential skin rash – first macular, then papular, vesicular, and scabbing within two weeks.^2,5,6Most cases are self-limiting and last two to three weeks²; treatment is therefore mostly supportive.⁷

Monkeypox was first isolated from monkeys in 1958, but it was not until 1970 that the first case in humans was reported.⁸ Since then, monkeypox has become endemic in Central Africa, particularly the Democratic Republic of Congo (DR Congo) where the case fatality rate (CFR) is 10.6%.^1,9Outbreaks outside Africa are rare but occurred in 2003 and 2022; it is postulated that cessation of smallpox vaccine administration, which could provide cross-protection against monkeypox, increased the likelihood of monkeypox outbreak.^6,10In just 10 days since 13^th May, 2022, the World Health Organization (WHO) has already been notified of over 250 laboratory-confirmed cases and suspected cases from 16 countries in Europe, North America, and Australia.^11,12Alarmingly, infected individuals denied any recent travel to Central Africa, unlike past cases.^11,13The surge of cases calls for immediate actions to halt the further spread.

Although no local cases of monkeypox have been reported in Hong Kong, inbound monkeypox-infected travellers pose a threat as they may initiate a local transmission chain.¹⁴Hong Kong has halted its smallpox vaccination program since WHO’s declaration of smallpox eradication in 1980^15,16, thus waning immunity against smallpox as observed in other countries is also a risk factor for a monkeypox outbreak in the territories.¹⁷ Should an outbreak occur, patient specimens will be obtained to determine the circulating monkeypox strain, since the CFR values of Central African and West African strains differ significantly (10% vs 1%-3.6%), implying contrasting prognoses.

As a developed region, Hong Kong is equipped with sufficient supportive facilities, isolation facilities and personal protective equipment.¹⁸Furthermore, nosocomial monkeypox transmission is unlikely In healthcare professionals as monkeypox are not as easily transmissible compared to airborne diseases such as COVID-19 and personal protective equipment is sufficient to break transmission chains. Monkeypox has a low mutation rate and is of stable transmissibility^19,20, as reassured by the WHO Smallpox Secretariat. Even if there are imported monkeypox cases, the number is expected to be “containable”.²¹

Nonetheless, efforts should be made to safeguard public health against monkeypox. Prevention relies on public health education; timely detection of local monkeypox transmission chain requires surveillance by private and public sexual health, red ribbon and dermatology clinics since clinics are likely MSM’s first point of contact and HIV is epidemiologically prevalent in MSM.^22,23 Any suspected case should be reported to the Hong Kong Centre for Health Protection.¹¹ Tecovirimat, an orthopoxviral vp37 envelope wrapping protein inhibitor²⁰, may be useful for monkeypox treatment according to primate studies but lacks corresponding in-human data from clinical studies.²⁴Future direction may include a restart of the vaccination programme and human clinical trials on tecovirimat, should monkeypox becomes a pandemic.

Reference

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The Washington Post. Expert: Monkeypox likely spread by sex at 2 raves in Europe. Available at: https://www.washingtonpost.com/world/expert-monkeypox-likely-spread-by-sex-at-2-raves-in-europe/2022/05/23/fdef8d88-da79-11ec-bc35-a91d0a94923b_story.html (Accessed 25 May 2022).

South China Morning Post. Hong Kong health authorities warn doctors to stay alert for suspected monkeypox cases. Available at: https://www.scmp.com/news/hong-kong/health-environment/article/3178860/hong-kong-health-authorities-warns-doctors-stay (Accessed 25 May 2022).

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The Guardian. Why are monkeypox cases suddenly emerging across the world and could the virus have mutated?. Available at: https://www.theguardian.com/world/2022/may/24/why-are-monkeypox-cases-suddenly-emerging-across-the-world-and-could-the-virus-have-mutated (Accessed 25 May 2022).

RTHK News. ‘Risk of monkeypox arriving in HK relatively low’. Available at: https://news.rthk.hk/rthk/en/component/k2/1649664-20220522.htm?spTabChangeable=0 (Accessed 25 May 2022).

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BBC News. Monkeypox virus outbreaks are containable – WHO. Available at: https://www.bbc.com/news/health-61553822 (Accessed 25 May 2022).

World Health Organization. Monkeypox – United Kingdom of Great Britain and Northern Ireland. Available at: https://www.who.int/emergencies/disease-outbreak-news/item/2022-DON383 (Accessed 25 May 2022).

Aids Concern. Men who have Sex with Men (MSM) Team. Available at: https://aidsconcern.org.hk/en/services/team-msm/ (Accessed 25 May 2022).

NIH National Library of Medicine: PubChem. Tecovirimat. Available at: https://pubchem.ncbi.nlm.nih.gov/compound/Tecovirimat (Accessed 25 May 2022).

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Disclaimer

This article is not medical advice. Patients should seek personal assessment by a licenced specialist. Physicians are recommended to read the full publication(s) as cited in the article before making medical decisions. This article does not supersede nor replace the published article(s).