Monkeypox

 

Monkeypox

Monkeypox is an infectious viral disease that can occur in humans and some other animals. Symptoms include fever, swollen lymph nodes, and a rash that forms blisters and then crusts over. The time from exposure to onset of symptoms ranges from 5 to 21 days. The duration of symptoms is typically 2 to 4 weeks. There may be mild symptoms, but to what extent it may occur without any symptoms is not known. The classic presentation of fever and muscle pains, followed by swollen glands, with lesions all at the same stage, has not been found to be common to all outbreaks. Cases may be severe, especially in children, pregnant women or people with suppressed immune systems.

The disease is caused by monkeypox virus, a zoonotic virus in the genus Orthopoxvirus. The variola virus, the causative agent of smallpox, was also in this genus. Of the two types in humans, the West African type causes a less severe disease than the Central African (Congo Basin) type. It may spread from handling bushmeat, animal bites or scratches, body fluids, contaminated objects, or other close contact with an infected person. Spread can occur by small droplets and possibly the airborne route. People can spread the virus from the onset of symptoms until all the lesions have scabbed and fallen off; with some evidence of spread for more than a week after lesions have crusted. The virus is believed to normally spread among certain rodents in Africa. Diagnosis can be confirmed by testing a lesion for the virus's DNA. The disease can appear similar to chickenpox.

There is no known cure. The smallpox vaccine was found to be around 85% protective in preventing infection in close contacts and in lessening the severity of the disease. A newer smallpox and monkeypox vaccine based on modified vaccinia Ankara has been approved, but with limited availability. Other measures include regular hand washing and avoiding sick people and other animals. Antiviral drugs, cidofovir and tecovirimat, vaccinia immune globulin and the smallpox vaccine may be used during outbreaks. The risk of death has varied from 0% to 11%. Most people recover.

The disease is no longer believed to be as rare as previously thought; possibly as a result of waning immunity since the stopping of routine smallpox vaccination. Cases have significantly increased since the 1980s. Sporadic cases occur frequently in Central and West Africa, and it is highly endemic in the Democratic Republic of the Congo (DRC). Hunters in the tropical forests of Central and West Africa are most at risk. It was first identified as a distinct illness in 1958 among laboratory monkeys in Copenhagen, Denmark. Monkeys are not a natural reservoir of the virus. The first cases in humans were found in 1970 in the DRC. An outbreak that occurred in the United States in 2003 was traced to a pet store where rodents imported from Ghana were sold. Since 2017, a large outbreak has been occurring in Nigeria. The 2022 monkeypox outbreak represents the first incidence of widespread community transmission outside of Africa, which was initially identified in the United Kingdom in May 2022, with subsequent cases confirmed in at least 20 countries in Europe, North America, South America, Asia, Africa, and Australia.

Definition and types

Monkeypox is a zoonotic poxvirus infection that can occur in both humans and some other animals. Two recognized distinct types are described as the Congo Basin clade and the milder West African clade.

Signs and symptoms

Stages of monkeypox lesion development

Early symptoms include headache, muscle pains, fever and fatigue. It may initially appear like influenza. The disease can resemble chickenpox, measles and smallpox but is distinguished by the presence of swollen glands. These characteristically appear behind the ear, below the jaw, in the neck or in the groin, before the onset of the rash. Within a few days of the fever, lesions characteristically appear on the face before appearing elsewhere such as palms of the hands and soles of the feet in a centrifugal distribution. Symptoms may vary in people with HIV. Many cases in the 2022 monkeypox outbreak presented with genital and peri-anal lesions, fever, swollen lymph nodes, and pain when swallowing.

Three-quarters of affected people have lesions on the palms and soles, more than two-thirds in the mouth, a third on the genitals and one in five have lesions in the eyes. They begin as small flat spots, before becoming small bumps which then fill with at first clear fluid and then yellow fluid, which subsequently burst and scab over. There may be a few lesions or several thousand, sometimes merging to produce large lesions.

In each affected part of the body, the lesions evolve in the same stage. It looks identical to the rash of smallpox. The rash typically lasts around ten days. An unwell person may remain so for two to four weeks. After healing, the lesions may leave pale marks before becoming dark scars.

Limited person-to-person spread of infection has been reported in disease-endemic areas in Africa.

Complications

Complications include secondary infections, pneumonia, sepsis, encephalitis, and loss of vision if severe eye infection. If infection occurs during pregnancy, still birth or birth defects may occur. The disease may be milder in people vaccinated against smallpox in childhood.

Causes

Monkeypox in both humans and animals is caused by infection with the monkeypox virus – a double-stranded DNA virus in the genus Orthopoxvirus, family Poxviridae. The virus is found mainly in tropical rainforest regions of Central and West Africa. The virus is split into Congo Basin and West African clades, matching the geographical areas.

Most human cases of monkeypox are acquired from an infected animal, though the route of transmission remains unknown. The virus is thought to enter the body through broken skin, the respiratory tract, or the mucous membranes of the eyes, nose, or mouth. Once a human is infected, transmission to other humans is common, with family members and hospital staff at particularly high risk of infection.

Human-to-human transmission is thought to occur primarily through close contact with an infected subject. There are indications that transmission occurs during sexual intercourse. Animal-to-human transmission may occur by bite or scratch, bush meat preparation, direct contact with body fluids or lesion material, or indirect contact with lesion material, such as through contaminated bedding.

Humans can be infected by an animal via a bite, or by direct contact with an infected animal’s bodily fluids. The virus can also spread from human to human, by respiratory (airborne) contact or by contact with an infected person's bodily fluids. Risk factors for transmission include sharing a bed or room, or using the same utensils as an infected person. Increased transmission risk is associated with factors involving the introduction of virus to the oral mucosa.

Monkeypox symptoms tend to begin 5 to 21 days after infection. Further research about the transmission of the strain responsible for the 2022 outbreak is ongoing, but it is not thought to be different to other strains of the West African clade.

Reservoir

In addition to monkeys, the virus is found in Gambian pouched rats (Cricetomys gambianus), dormice (Graphiurus spp.) and African squirrels (Heliosciurus, and Funisciurus). The use of these animals as food may be an important source of transmission to humans.

No specific reservoir for monkeypox has been found. Monkeys are not a main reservoir, contrary to the name. It is believed African rodents, such as the ones listed above, serve as the actual reservoir.

Diagnosis

Clinical differential diagnosis must consider other rash illnesses, such as chickenpox, measles, bacterial skin infections, scabies, syphilis and medication-associated allergies. Lymphadenopathy during the prodromal stage of illness can distinguish monkeypox from chickenpox or smallpox. Diagnosis can be verified by testing for the virus.

Polymerase chain reaction (PCR) testing of samples from skin lesions is the preferred laboratory test. PCR blood tests are usually inconclusive because the virus does not remain very long in the blood. To interpret test results, information is required on date of onset of fever, date of onset of rash, date of specimen collection, current stage of rash, and patient age.

Prevention

Vaccination against smallpox is assumed to provide protection against human monkeypox infection because they are closely related viruses and the vaccine protects animals from experimental lethal monkeypox challenges. This has not been conclusively demonstrated in humans because routine smallpox vaccination was discontinued following the eradication of smallpox.

Smallpox vaccine has been reported to reduce the risk of monkeypox among previously vaccinated persons in Africa. The decrease in immunity to poxviruses in exposed populations is a factor in the prevalence of monkeypox. It is attributed both to waning cross-protective immunity among those vaccinated before 1980 when mass smallpox vaccinations were discontinued, and to the gradually increasing proportion of unvaccinated individuals.

The United States Centers for Disease Control and Prevention (CDC) recommends that persons investigating monkeypox outbreaks and involved in caring for infected individuals or animals should receive a smallpox vaccination to protect against monkeypox. Persons who have had close or intimate contact with individuals or animals confirmed to have monkeypox should also be vaccinated.

The CDC does not recommend pre-exposure vaccination for unexposed veterinarians, veterinary staff, or animal control officers, unless such persons are involved in field investigations.

The CDC recommends that healthcare providers don a full set of personal protective equipment (PPE) before caring for an infected person. This includes a gown, mask, goggles, and a filtering disposable respirator (such as an N95). An infected person should be isolated in preferably a negative air pressure room or at least a private exam room to keep others from possible contact.

Treatment

In the European Union and the United States, tecovirimat is approved for the treatment of several poxviruses, including monkeypox.[55] BMJ Best Practice recommends tecovirimat or the smallpox treatment brincidofovir as the first line antiviral treatment if required, alongside supportive care (including antipyretic, fluid balance and oxygenation). Empirical antibiotic therapy or aciclovir may be used if secondary bacterial or varicella zoster infection is suspected, respectively.

Outcome

After healing, the scabs may leave pale marks before becoming darker scars. The risk of death in those infected ranges from 0% to 11%, depending on the type of monkeypox and location in the world. Fatality rates have been reported as around 3.6% in West Africa and 10.6% in Central Africa. Most reported deaths have occurred in young children and people with HIV.