Information about the mpox disease

The virus was first discovered in monkeys, which was why it was named the monkeypox virus. The disease, which was first detected in a human in 1970, was named monkeypox. Despite the name, the virus has primarily been found in various kinds of rodents in Central and West Africa.

What causes mpox, and how does the disease spread?

Mpox is caused by the monkeypox virus, a species of orthopoxvirus. There are two types of monkeypox virus: clade 1 and clade 2, which are in turn divided into sub-clades 1a and 1b and sub-clades 2a and 2b respectively. Clade 1 has been reported as being more serious, with a significantly higher mortality than clade 2. Clade 1 is also more contagious.

Before 2022, the most commonly described transmission route was from animals to humans. In rare cases, the infection was transmitted through close contact between humans. Since 2022, mpox (clade 2b) has for the first time been spreading to a greater extent, also outside Africa. The disease has mainly affected men who have sex with men (MSM), and the infection has primarily been spread via sexual contact.

Since late autumn 2023, clade 1 has been spreading in Central Africa, with a rapidly increasing number of cases, especially in the Democratic Republic of Congo. By August 2024, the outbreak of clade 1 has spread to several countries in Africa. In the outbreak of mpox clade 1 in Africa, infection routes are reported primarily from person to person, via close skin contact, as well as sexual contact.

The virus is transmitted primarily through close physical contact with a person who is infected. Physical sexual contact, or other close skin contact with an infected person, constitutes a particularly high risk. The infection can spread without sexual contact, for example within families.

The virus may also be present in the respiratory tract, which means that infection from the respiratory tract cannot be completely ruled out.

There have been a small number of cases of indirect transmission of the virus, such as via bedding, towels and sex toys that a person with mpox has been in contact with. The virus can also spread from mother to newborn child, primarily in connection with childbirth. In individuals with mpox, the monkeypox virus can be found in seminal fluid or vaginal secretions.

According to data available, healthcare and laboratory staff are at very low risk of being infected with the monkeypox virus in their professional activities. In the global outbreak of mpox clade 2 that started in 2022, isolated cases of infection in the healthcare sector were reported, but only after specific incidents such as puncture wounds. For the ongoing clade 1 outbreak, there is still some uncertainty about infectivity, and therefore whether the risk to healthcare and laboratory staff differs in any significant way compared with clade 2.

Symptoms and treatment

The time from a person becoming infected until they develop symptoms (the incubation period) is usually 6 to 13 days. But it can be both shorter and longer (up to 21 days).

Symptoms may differ, depending on the way in which the infection was transmitted. The following symptoms are common in non-sexual transmission:

• Blisters or sores, often on the trunk, arms, legs, hands and feet.

In addition to this, people may also experience:

• fever
• headaches and muscle aches
• swollen lymph nodes.

In the case of sexual transmission, the following symptoms are also common:

• Blisters or sores on the face, or in and around the mouth and in the throat.
• Blisters or sores on and around the genitals and around the anus.
• Problems with bowel movements, such as diarrhoea, and difficulty in urinating.
• Pain around the anus and in the rectum.
• A feeling of heaviness in the lower abdomen and the pelvis.

The disease can cause a lot of pain and discomfort, but usually heals on its own within two to four weeks. People with weakened immune systems may experience a longer period of illness. Adult, immune-healthy people rarely become seriously ill. People with mpox sometimes need to be admitted to hospital, for example due to difficulties in eating because of painful blisters in the mouth.

Both younger children and pregnant women and people with weakened immune systems are considered to be at greater risk of becoming seriously ill if they are infected with the monkeypox virus. In rare cases, usually in people with weakened immune systems, the disease can result in complications.

There are drugs that are effective against the infection and recommended in the event of serious illness.

Epidemiological surveillance and microbiological diagnostics

The disease is being monitored by the Public Health Agency of Sweden through infection control notifications and external monitoring. Suspicions of mpox may arise based on symptoms and whether a person has been exposed to the risk of infection. The diagnosis is confirmed after sampling by detecting the virus’s DNA in a laboratory analysis (molecular biological analysis using PCR).

Preventive measures

It is possible to prevent infection by avoiding close contact with infected people. Having a large number of sexual contacts poses a particularly high risk of infection. There are recommendations both for those travelling to Sweden from regions where infection is spreading and for those planning to travel to such regions.

Recommendations for travellers due to the spread of mpox

There is a vaccine that provides good protection against mpox. Vaccination is recommended for people who have been exposed to the virus or have an increased risk of exposure to the monkeypox virus.

Vaccines, together with other infection control measures, such as good access to testing for the disease, contact tracing and rules of conduct for sick and exposed individuals, are considered to be effective in reducing the spread of infection.

If you experience symptoms that may be consistent with mpox, or if you become aware that you have been in close contact with a person who has mpox, it is important to make contact with the healthcare service to have an assessment and, if necessary, to be tested. If you have been in a region with an ongoing spread of mpox, it is important to look out for clear symptoms of mpox, such as painful blisters and sores, for three weeks after you have returned home.

Vaccination against mpox (in Swedish)

Measures in the event of a case or an outbreak

There is the possibility of offering a vaccine after exposure, and this should ideally take place within four days of the time of exposure.

According to the Swedish Communicable Diseases Act, mpox is a generally hazardous disease that is notifiable for infection tracing, which means, among other things, that a person who suspects that they have mpox has an obligation to seek care. It also means that infection control measures such as contact tracing and rules of conduct are used to limit the spread. All cases of mpox must be reported to the county medical officer and to the Public Health Agency of Sweden.

Remarks

The disease changed its name to mpox in Sweden on 1 January 2023, after the World Health Organization (WHO) recommended the name change. Work on a possible name change of the virus is ongoing, but at present it continues to be called the monkeypox virus.

Further reading

• Mpox (cdc.gov)
• Mpox (who.int)
• Factsheet for health professionals on mpox (ecdc.europa.eu)