Monday, May 16, 2022

WHO Update & Risk Assessment On the UK's imported Monkeypox Case

Geographic Range of Monkeypox - Credit WHO


Just over a week ago the UK reported an imported case of Monkeypox (see UK Reporting Another Imported (ex Nigeria) Case of Monkeypox) in a traveller returning from Nigeria, which is one of a handful of West and Central African nations where the virus is endemic (see map above). 

This case should not be confused with the two cases announced on Saturday (May 14th)  by the UK, which are reportedly not connected to this imported case, and whose origins remains under investigation. 

While relatively rare, in recent years the UK has reported more than a half dozen imported cases (see here, here, and here), and last year the United States reported two separate imported cases (see here and here).  Other countries, including Singapore and Israel, have reported imported cases as well. 

In response to the recent rise - and geographic spread - of Monkeypox cases, over the past 3 years we've seen several reports on the increasing threat from this virus, and the approval - in 2019 - of a new Monkeypox vaccine by the FDA

PLoS NTD: The Changing Epidemiology of Human Monkeypox—A potential threat?

EID Journal: Reemergence of Human Monkeypox and Declining Population Immunity - Nigeria, 2017–2020

WHO: Modelling Human-to-Human Transmission of Monkeypox

Currently the WHO's Outbreaks and Emergencies Bulletin, Week 17: 18 - 24 April 2022 for the continent of Africa mentions 4 countries (Cameroon, CAR, DRC & Nigeria)  where  Monkeypox has been reported in recent months, although the number of cases is small, and are likely under-reported. 

While we await word on the two most recent cases in the UK, we have the following update and risk assessment from the WHO on the previous imported case. 
Monkeypox - United Kingdom of Great Britain and Northern Ireland
16 May 2022

Situation at a glance

On 7 May 2022, WHO was informed of a confirmed case of monkeypox in an individual who travelled from the United Kingdom to Nigeria.

The case developed a rash on 29 April 2022 and returned to the United Kingdom on 4 May. Monkeypox was suspected and the case was immediately isolated. As of 11 May, extensive contact tracing has been undertaken to identify exposed contacts in healthcare settings, the community and the international flight. These individuals are being followed up for 21 days from the date of last exposure with the case. None has reported compatible symptoms so far.

Since the case was immediately isolated and contact tracing was performed, the risk of onward transmission related to this case in the United Kingdom is minimal. However, as the source of infection in Nigeria is not known, there remains a risk of ongoing transmission in this country.

Description of the case

On 7 May 2022, the National IHR Focal Point for the United Kingdom notified WHO of a confirmed case of monkeypox in an individual who travelled from United Kingdom to Nigeria from late April to early May 2022 and stayed in Lagos and Delta States in Nigeria. The case developed a rash on 29 April and returned to the United Kingdom, arriving on 4 May. On the same day (4 May), the case presented to hospital. Based on the travel history and rash illness, monkeypox was suspected at an early stage and the case was isolated immediately. Appropriate use of personal protective equipment was ensured during hospitalization. Monkeypox (West African clade) was laboratory confirmed by reverse transcriptase polymerase chain reaction (RT-PCR) on a vesicular swab on 6 May by the United Kingdom Health Security Agency (UKHSA) Rare and Imported Pathogens Laboratory.

Epidemiology of the disease

Monkeypox is a sylvatic zoonosis with incidental human infections that usually occur sporadically in forested parts of Central and West Africa. It is caused by the monkeypox virus which belongs to the orthopoxvirus family. Monkeypox can be transmitted by contact and droplet exposure via exhaled large droplets. The incubation period of monkeypox is usually from 6 to 13 days but can range from 5 to 21 days. The disease is often self-limiting with symptoms usually resolving spontaneously within 14 to 21 days. Symptoms can be mild or severe, and lesions can be very itchy or painful. The animal reservoir remains unknown, although is likely to be among rodents. Contact with live and dead animals through hunting and consumption of wild game or bush meat are known risk factors.

There are two clades of monkeypox virus, the West African clade and Congo Basin (Central African) clade. Although the West African clade of monkeypox virus infection sometimes leads to severe illness in some individuals, disease is usually self-limiting. The case fatality ratio for the West African clade has been documented to be around 1%, whereas for the Congo Basin clade, it may be as high as 10%. Children are also at higher risk, and monkeypox during pregnancy may lead to complications, congenital monkeypox or stillbirth.

Milder cases of monkeypox may go undetected and represent a risk of person-to-person transmission. There is likely to be little immunity to the infection in those travelling and exposed as endemic disease is geographically limited to parts of West and Central Africa. While a vaccine has been approved for prevention of monkeypox, and traditional smallpox vaccine also provides protection, these vaccines are not widely available and populations worldwide under the age of 40 or 50 years no longer benefit from the protection afforded by prior smallpox vaccination programmes.

Public health response
• Health authorities in the United Kingdom have set up an incident management team to coordinate identification and management of contacts.
• As of 11 May, extensive contact tracing has identified exposed contacts in the community, the healthcare setting and on the international flight. None has reported compatible symptoms so far.
• All identified contacts have been assessed and classified based on their exposure to the case and are being followed up accordingly through either active or passive surveillance for 21 days after their last exposure to the case. Post-exposure prophylaxis with vaccination is being offered to the higher risk contacts.
• Nigerian authorities were informed about this case and travel history in Nigeria on 7 May. The case did not report contact with anyone with a rash illness or known monkeypox in Nigeria. Details of travel and contacts within Nigeria have been shared with authorities in Nigeria for follow up as necessary.
WHO risk assessment

In the United Kingdom, there have been seven cases of monkeypox previously reported; all importations were related to a travel history to or from Nigeria. In 2021, there were also two separate human monkeypox cases imported from Nigeria reported by the United States of America.

Since September 2017, Nigeria has continued to report cases of monkeypox. From September 2017 to 30 April 2022, a total of 558 suspected cases have been reported from 32 states in the country. Of these, 241 were confirmed cases, and among these there were eight deaths recorded (Case Fatality Ratio: 3.3%). From 1 January to 30 April 2022, 46 suspected cases have been reported of which 15 were confirmed from seven states - Adamawa (three cases), Lagos (three cases), Cross River (two cases), Federal Capital Territory (FCT) (two cases), Kano (two cases), Delta (two cases) and Imo (one case). No death has been recorded in 2022.

In the present case, the source of infection is currently unknown and the risk of further transmission in Nigeria cannot be excluded. Once monkeypox was suspected in the United Kingdom, authorities promptly initiated appropriate public health measures, including isolation of the case and contact tracing. The risk of potential onward spread related to this case in the United Kingdom is therefore minimal. As the source of infection in Nigeria is not known, there remains a risk of further transmission in Nigeria.

Importations of monkeypox from an endemic country to another country has been documented on eight previous occasions. In this instance, the confirmed case has a history of travel from Delta state in Nigeria, where monkeypox is endemic.

WHO advice

Any illness during travel or upon return from an endemic area should be reported to a health professional, including information about all recent travel and immunization history. Residents and travelers to endemic countries should avoid contact with sick animals (dead or alive) that could harbour monkeypox virus (rodents, marsupials, primates) and should refrain from eating or handling wild game (bush meat). The importance of hand hygiene using soap and water, or alcohol-based sanitizer should be emphasized. While a vaccine and specific treatment have recently been approved for monkeypox, in 2019 and 2022 respectively, these countermeasures are not yet widely available.

A patient with monkeypox should be isolated and provided with supportive care during the presumed and known infectious periods, that is during the prodromal (early signs) and rash stages of the illness, respectively. Timely contact tracing, surveillance measures and raising awareness of imported emerging diseases among health care providers are essential for preventing further secondary cases and effective management of monkeypox outbreaks.

Health workers caring for patients with suspected or confirmed monkeypox should implement standard, contact and droplet infection control precautions. This includes all workers such as cleaners and laundry personnel who may be exposed to the patient care setting, bedding, towels, or personal belongings. Samples taken from people with suspected monkeypox or animals with suspected monkeypox virus infection should be handled by trained staff working in suitably equipped laboratories.

International travel and trade: WHO does not recommend any restriction for travel to and trade with Nigeria or the United Kingdom based on available information at this time.

While the two known clades of Monkeypox remain poorly transmissible, these viruses continue to evolve and diversify, and as discussed in the 2014 EID Journal article Genomic Variability of Monkeypox Virus among Humans, Democratic Republic of the Congo:

Small genetic changes could favor adaptation to a human host, and this potential is greatest for pathogens with moderate transmission rates (such as MPXV) (40). The ability to spread rapidly and efficiently from human to human could enhance spread by travelers to new regions.

So we monitor their progress with considerable interest.