Mpox (monkeypox) Virus Smallpox

Key facts

Mpox (monkeypox)

1) Mpox (monkeypox) is a viral illness caused by the monkeypox virus, a species of the genus Orthopoxvirus. Two different clades exist: clade I and clade II

2) Common symptoms of mpox are a skin rash or mucosal lesions which can last 2–4 weeks accompanied by fever, headache, muscle aches, back pain, low energy, and swollen lymph nodes.

3) Mpox can be transmitted to humans through physical contact with someone who is infectious, with contaminated materials, or with infected animals.

4) Laboratory confirmation of mpox is done by testing skin lesion material by PCR.

5) Mpox is treated with supportive care. Vaccines and therapeutics developed for smallpox and approved for use in some countries can be used for mpox in some circumstances.

6) In 2022–2023 a global outbreak of mpox was caused by a strain known as clade IIb.

7) Mpox can be prevented by avoiding physical contact with someone who has mpox. Vaccination can help prevent infection for people at risk.

Overview

Mpox (monkeypox) is an infectious disease caused by the monkeypox virus. It can cause a painful rash, enlarged lymph nodes and fever. Most people fully recover, but some get very sick. The WHO defines smallpox as “an acute contagious disease caused by the variola virus, a member of the ortho poxvirus family.” Although smallpox was first documented in ancient Egyptian mummies, it is suspected that the disease has been around for a minimum of 3,000 years.

Anyone can get mpox. It spreads from contact with infected:

• persons, through touch, kissing, or sex
• animals, when hunting, skinning, or cooking them
• materials, such as contaminated sheets, clothes or needles
• pregnant persons, who may pass the virus on to their unborn baby.

If you have mpox:

• Tell anyone you have been close to recently
• Stay at home until all scabs fall off and a new layer of skin forms
• Cover lesions and wear a well-fitting mask when around other people
• Avoid physical contact.

The disease mpox (formerly monkeypox) is caused by the monkeypox virus (commonly abbreviated as MPXV), an enveloped double-stranded DNA virus of the Orth poxvirus genus in the Poxviridae family, which includes variola, cowpox, vaccinia and other viruses. The two genetic clades of the virus are clades I and II.

The monkeypox virus was discovered in Denmark (1958) in monkeys kept for research and the first reported human case of mpox was a nine-month-old boy in the Democratic Republic of the Congo (DRC, 1970). Mpox can spread from person to person or occasionally from animals to people. Following eradication of smallpox in 1980 and the end of smallpox vaccination worldwide, mpox steadily emerged in central, east and west Africa. A global outbreak occurred in 2022–2023. The natural reservoir of the virus is unknown – various small mammals such as squirrels and monkeys are susceptible.

History of Smallpox

The CDC provides a brief overview of the historical spread of smallpox: In the sixth century, it is thought that trade led to the introduction of smallpox in Japan, and it wasn’t until the seventeenth century that European settlers brought smallpox to North America.

According to the CDC, in the United States, the last smallpox outbreak occurred in 1949. However, the last global outbreak of the disease was not until nearly 20 years later, in 1977.

The WHO states that eradication of smallpox occurred when “widespread immunization and surveillance were conducted around the world for several years. The last known natural case was in Somalia in 1977. In 1980, the WHO declared smallpox eradicated — the only infectious disease to achieve this distinction. This remains among the most notable and profound public health successes in history.”

Signs and symptoms

Mpox causes signs and symptoms which usually begin within a week but can start 1–21 days after exposure. Symptoms typically last 2–4 weeks but may last longer in someone with a weakened immune system. The symptoms of smallpox include fever, fatigue, back pain, abdominal pain, and vomiting in the early stages. Within three days of infection, the patients will develop a rash with liquid-filled bumps, typically beginning on the face and hands but can spread all over the body.

Smallpox transmission occurs from close person-to-person contact and has an incubation period between 1 week and 17 days.

Historically, approximately 30% of cases were fatal.

Common symptoms of mpox are:

• rash
• fever
• sore throat
• headache
• muscle aches
• back pain
• low energy
• swollen lymph nodes.

For some people, the first symptom of mpox is a rash, while others may have different symptoms first. The rash begins as a flat sore which develops into a blister filled with liquid and may be itchy or painful. As the rash heals, the lesions dry up, crust over and fall off.

Some people may have one or a few skin lesions and others have hundreds or more. These can appear anywhere on the body such as the:

• palms of hands and soles of feet
• face, mouth and throat
• groin and genital areas
• anus.

Phases(smallpox)

The CDC suggests that the average incubation period for this disease is 10 days to 2 weeks. During the incubation period, people typically have no symptoms. The first stage of smallpox can last between two and four days. At this stage, patients can be contagious and typically experience symptoms such as fever, headaches, body aches, and vomiting. This stage of illness is when patients cannot proceed as usual.

The next stage, also known as the most contagious stage, is when rashes begin to appear. At first, the small red spots start on the tongue and mouth. These spots become sores and can spread to the face, arms, legs, hands, and feet. The CDC states, “by the fourth day, the skin sores fill with a thick, opaque fluid and often have a dent in the center.

Once the skin sores fill with fluid, the fever may rise again and remain high until scabs form over the bumps. “The next phase is the pustular rash and scab stage. At this point, “The sores become pustules (sharply raised, usually round and firm to the touch, like peas under the skin). After about five days, the pustules begin to form a crust and then scab. By the end of the second week, after the rash appears, most of the sores have scabbed over.”

The scabs will then begin to fall off until there are no more, at which point the patient will no longer be contagious.

Transmission

While the disease is thought not to become contagious until the first sores appear, the virus is spread by respiratory droplets from coughing or sneezing. The patients do not stop being contagious until the last scab falls off. In addition to direct contact spreading the disease, indirect contact with materials contaminated by patients can also spread the virus. This disease is contained to the human species and has yet to be discovered in insects or animals.

Prevention and Treatment

The smallpox vaccine was first developed in 1796 by Edward Jenner. At one point, the smallpox vaccine was widely administered; however, since the eradication of the disease, the vaccines are not widely recommended. According to the CDC, the virus uses vaccinia, a pox virus like smallpox. The vaccine can provide varying forms of protection depending on when it is administered. The FDA approved Tecovirimat and Brin cidofovir as antivirals for the treatment of smallpox.

Diagnosis

Identifying mpox can be difficult as other infections and conditions can look similar. It is important to distinguish mpox from chickenpox, measles, bacterial skin infections, scabies, herpes, syphilis, other sexually transmissible infections, and medication-associated allergies. Someone with mpox may also have another sexually transmissible infection such as herpes. Alternatively, a child with suspected mpox may also have chickenpox. For these reasons, testing is key for people to get treatment as early as possible and prevent further spread.

Detection of viral DNA by polymerase chain reaction (PCR) is the preferred laboratory test for mpox. The best diagnostic specimens are taken directly from the rash – skin, fluid or crusts – collected by vigorous swabbing. In the absence of skin lesions, testing can be done on oropharyngeal, anal or rectal swabs. Testing blood is not recommended. Antibody detection methods may not be useful as they do not distinguish between different Orth poxviruses.

Treatment and vaccination

The goal of treating mpox is to take care of the rash, manage pain and prevent complications. Early and supportive care is important to help manage symptoms and avoid further problems. Getting an mpox vaccine can help prevent infection. The vaccine should be given within 4 days of contact with someone who has mpox (or within up to 14 days if there are no symptoms).

It is recommended for people at high risk to get vaccinated to prevent infection with mpox, especially during an outbreak. This includes:

• health workers at risk of exposure
• men who have sex with men
• people with multiple sex partners
• sex workers.

Outbreaks

After 1970, mpox occurred sporadically in Central and East Africa (clade I) and West Africa (clade II). In 2003 an outbreak in the United States of America was linked to imported wild animals (clade II). Since 2005, thousands of suspected cases are reported in the DRC every year. In 2017, mpox re-emerged in Nigeria and continues to spread between people across the country and in travellers to other destinations. Data on cases reported up to 2021 are available here.

In May 2022, an outbreak of mpox appeared suddenly and rapidly spread across Europe, the Americas and then all six WHO regions, with 110 countries reporting about 87 thousand cases and 112 deaths. The global outbreak has affected primarily (but not only) gay, bisexual, and other men who have sex with men and has spread person-to-person through sexual networks. More information on the global outbreak is available here with detailed outbreak data here;

In 2022, outbreaks of mpox due to Clade I MPXV occurred in refugee camps in the Republic of the Sudan. A zoonotic origin has not been found.

WHO response

The global outbreak of mpox was declared a public health emergency of international concern (PHEIC) on 23 of July 2022. WHO published a strategic preparedness and response plan for mpox and a suite of technical guidance documents. Surveillance, diagnostics, risk communication and community engagement remain central to stopping the outbreak and eliminating human-to-human transmission of mpox in all contexts.

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