Geographic Range of Monkeypox - Credit WHO
#16,089
Twelve days ago we learned of 2020's second high profile exported case of Monkeypox from Nigeria (see CDC & Texas Confirm Monkeypox In US Traveler ex Nigeria), following an earlier case last May in the UK (see ECDC CDTR: 3rd Monkeypox Case In the UK) which resulted in two secondary cases.
Monkeypox, which is endemic in parts of West and Central Africa, has been on the ascendent for the past couple of decades, as immunity from long-discontinued smallpox vaccinations has waned. In recent years we've seen exported cases - and rare secondary transmission - reported in the UK, Singapore, and Israel.
Although the primary animal reservoir for Monkeypox is unknown, humans can become infected in the wild from an animal bite or direct contact with the infected animal’s blood, body fluids, or lesions, but consumption of under cooked bushmeat is also suspected as an infection risk. Human-to-human transmission is also possible.
The disease also can be spread from person to person, but it is much less infectious than smallpox. The virus is thought to be transmitted by large respiratory droplets during direct and prolonged face-to-face contact. In addition, monkeypox can be spread by direct contact with body fluids of an infected person or with virus-contaminated objects, such as bedding or clothing.According to the CDC there are two distinct genetic groups (clades) of monkeypox virus—Central African and West African. West African monkeypox - such as has been spreading recently in Nigeria - is associated with milder disease, fewer deaths, and limited human-to-human transmission.
Research over the past few years suggests that Monkeypox outbreaks are becoming more frequent, and getting larger, potentially increasing its threat to public health. A few recent reports include:
WHO Update & Risk Assessment On Monkeypox In The DRC
WHO: Modelling Human-to-Human Transmission of Monkeypox
Late yesterday the WHO published their 3rd Monkeypox Update since early June, describing the latest case exported to the United States. I'll have a brief postscript after the break.
Monkeypox - United States of America
27 July 2021
On 17 July 2021, the IHR National Focal Point of the United States of America (USA) notified PAHO/WHO of an imported case of human monkeypox in Dallas, Texas, USA. The case-patient travelled from the USA to Lagos State, Nigeria on 25 June and also stayed in Ibadan, Oyo State, from 29 June to 3 July. He developed self-reported fever, vomiting and mild cough on 30 June, and a painful genital rash on 7 July. The case-patient returned to the USA, departing Lagos on 8 July and arriving on 9 July. He developed a facial rash on the next day. On 13 July, the patient attended a local hospital; fever was documented, and he was immediately placed under isolation.
Sample of a skin lesion was taken, and on 14 July, an Orthopoxvirus was confirmed by reverse transcriptase polymerase chain reaction (RT-PCR) by Dallas County. On 15 July, the patient’s skin samples tested positive for the West African clade of monkeypoxvirus via RT-PCR conducted at the US Centers for Disease Control and Prevention (US CDC) Poxvirus and Rabies Branch Laboratory. The patient is currently hospitalized.
At this time, the source of infection for this case is unknown. Although monkeypox is considered a zoonotic disease, the wildlife reservoir has not been determined. During an outbreak of monkeypox in human in 2003 in the USA, exposure was traced to contact with pet prairie dogs that had been co-housed with monkeypoxvirus-infected African rodents, imported from Ghana. Contact with wild animals (including live animals, meat for consumption, and other products) are known potential risk factors in enzootic countries. Prolonged contact with an infected person can also result in person-to-person transmission.
An outbreak occurred in Nigeria from 2017 to 2019, with cases still being reported in 2021. In addition to Nigeria, outbreaks have also been reported in nine other countries in central and western Africa since 1970. In 2020, over 6200 suspected cases were reported in the Democratic Republic of the Congo. Sporadic outbreaks among humans have occurred in other countries such as Cameroon or the Central African Republic.
This is the first time that human monkeypox has been detected in a traveller to the USA, and the first case reported in the USA since the outbreak in 2003. Human monkeypox in travellers from Nigeria has been documented on seven previous occasions since 1978. The earliest documented travel-related case occurred in Benin in a patient who had contracted the infection in Oyo State, Nigeria. Since 2018, six cases have been reported and confirmed in non-endemic countries via travelers to Israel (2018), Singapore (2019), and the United Kingdom of Great Britain and Northern Ireland (two cases in 2018, one in 2019 and one in 2021). Lagos State and Oyo State in Nigeria continue to report and confirm sporadic cases. Additionally, cases have been reported in South Sudan which were likely imported from the Democratic Republic of the Congo.Public health responsePublic health measures are being taken, including isolation and treatment of the patient. The US CDC and state and local health departments are monitoring possible community and health care contacts who, during the infectious periods, had contact with the case-patient. The US CDC is working with the airline and state and local health officials to contact airline passengers who shared a common seating area with the patient during his travel from Nigeria and within the USA.Travellers on these flights were required to wear masks due to the ongoing COVID-19 pandemic. While the risk of spread of monkeypox via respiratory droplets to others on the flights is therefore considered low, contamination of common use areas such as toilets may have occurred. Health personnel involved in the patient’s care have been wearing appropriate personal protective equipment. Post-exposure vaccination with a smallpox vaccine within 14 days from the most recent contact with the case-patient may be recommended for some contacts. As of 25 July, over 200 persons are being monitored in the USA and none have developed symptoms consistent with monkeypox.The surveillance and public health response in Nigeria for the re-emergence of monkeypox since 2017 is ongoing across the country. Outbreak investigation related to this case is focused on Lagos and Oyo States and involves human and animal health specialists to identify possible sources of exposure and monitor persons who may have been in contact with the reported case.WHO risk assessmentMonkeypox 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 (MPXV) that belongs to the Orthopoxvirus family. Genomic sequencing shows there are two monkeypox clades – Congo Basin and West African – consistent with observed differences in human pathogenicity and fatality in the two geographic areas. Both clades can be transmitted by contact and droplet exposure via exhaled large droplets, or via fomites such as bedding, and can be fatal in humans.The incubation period for 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 14-21 days. Symptoms can be mild or severe, and lesions can be painful and become itchy. Although the West African clade of monkeypox virus infection generally causes mild disease, it may lead to severe illness in some individuals. The case fatality rate for the West African clade is around 1% while it may be as high as 10% for the Congo Basin clade. Immune deficiency appears to be a risk factors for severe disease. 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. Increased susceptibility to monkeypox is in part related to waning immunity due to cessation of smallpox immunization.The animal reservoir remains unknown, although is likely to be among small mammals. Contact with live and dead animals through hunting and consumption of wild game or bush meat are presumed drivers of human infection.
This is the first imported case detected in a traveler to the United States, but in 2003 we saw a rare multi-state (Illinois, Indiana, Kansas, Missouri, Ohio, and Wisconsin) outbreak when a Texas animal distributor imported hundreds of small animals from Ghana, which in turn infected prairie dogs that were subsequently sold to the public (see MMWR Update On Monkeypox 2003).
By the time that outbreak was quashed, the U.S. saw 37 confirmed, 12 probable, and 22 suspected human cases. Among the confirmed cases 5 were categorized as being severely ill, while 9 were hospitalized for > 48 hrs; although no patients died (cite).
Like all viruses, Monkeypox continues to evolve and diversify, as discussed in the 2014 EID Journal article Genomic Variability of Monkeypox Virus among Humans, Democratic Republic of the Congo, where the authors cautioned:
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.
All of which makes Monkeypox one of the emerging zoonotic viruses we watch with considerable interest.
