Noticias sobre brotes de enfermedades

Viruela del mono - Estados Unidos de América

27 de julio de 2021
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Descripción de la situación

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.

Respuesta de salud pública

Public 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.

Evaluación del riesgo por la OMS

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 (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. 

Consejos de la OMS

Any illness during travel in an endemic area or upon return should be reported to a health professional, including information about all recent travel and immunization history. Residents and travellers to endemic countries should avoid contact with sick, dead or live animals that could harbor 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.

Patient care for monkeypox is symptom-based optimal care. A patient with monkeypox should be provided with supportive care and treatment of underlying conditions and complications. In some circumstances, specific antiviral treatment approved for smallpox may be offered on a compassionate or emergency use basis.

A patient with monkeypox should be isolated during the infectious period, just prior to and including the rash stage of the infection until all lesions have crusted and fallen off. Timely contact-tracing, surveillance measures and raising awareness of emerging diseases among health care providers are essential to effectively manage monkeypox outbreaks and prevent secondary cases.

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 and animals with suspected monkeypox virus infection should be handled by trained staff working in suitably equipped laboratories.

WHO does not recommend any restriction for travel to, or trade with, Nigeria or the USA based on available information at this time.

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