Understanding Monkeypox and the Spread of Outbreaks


The global eradication of smallpox more than 40 years ago was one of the greatest achievements in public health history, eliminating a cause of death, blindness and disfigurement that had plagued mankind for at least less than 3000 years old. But, on the other hand, it also led to the end of a global vaccination program that offered protection against other smallpox viruses. This includes monkeypox, which has spread from its animal hosts to infect humans in Africa with increasing frequency since the 1970s. Monkeypox now poses a serious and evolving threat after sparking epidemics in dozens of countries this year, mainly in Europe, again demonstrating how easily an infectious agent that emerges in one country can quickly become an international concern.

Monkeypox is a misnomer resulting from the fact that it was first discovered at the Statens Serum Institut in Copenhagen in 1958, when outbreaks of a smallpox-like disease occurred in monkeys kept for research. Although monkeys are susceptible to it, just like humans, they are not the source. The virus belongs to the genus Orthopoxvirus, which includes variola virus, the cause of smallpox; vaccinia virus, which is used in the smallpox vaccine; and vaccinia virus. Monkeypox is less contagious than smallpox and symptoms are milder. About 30% of smallpox patients have died, while the death rate from monkeypox in recent times is around 3% to 6%, according to the World Health Organization.

2. What does monkeypox do?

After an incubation period of about one to two weeks, the illness usually begins with fever, muscle aches, fatigue, and other flu-like symptoms. Unlike smallpox, monkeypox also causes swelling of the lymph nodes. A few days after the onset of fever, patients develop a rash, often starting on the face and then spreading to other parts of the body. The lesions turn into fluid-containing pustules that form a crust. If a lesion forms on the eye, it can cause blindness. The illness usually lasts two to four weeks, according to the WHO. The person is contagious from the time the symptoms appear until the scabs fall off and the sores heal. Mortality is higher in children and young adults, while people with weakened immune systems are particularly at risk of severe disease. Pregnancy also carries a high risk of serious congenital infection, pregnancy loss, and maternal morbidity and mortality.

3. How is it normally transmitted?

Monkeypox does not usually spread easily between people. Contact with the virus from an animal, human or contaminated object is the primary route. The virus enters the body through damaged skin, the respiratory tract or the mucous membranes of the eyes, nose or mouth. Person-to-person transmission is thought to occur through respiratory particles during direct and prolonged face-to-face contact. Vertical transmission from mother to unborn child has also been documented. It can also occur through contact with bodily fluids or lesion material, or indirectly through contact with contaminated clothing or linens. Common household disinfectants can kill it.

4. What’s unusual this time around?

There have been several chains of human-to-human transmission, including through sexual networks, in countries where monkeypox is not normally present.

• The cases do not involve recent travel to places in West and Central Africa, where the disease is endemic.

• Although anyone can get monkeypox, most cases occur in humans. In endemic areas of Africa this was thought to be linked to hunting practices, whereas in the current epidemic most individuals are males between the ages of 21 and 40 who have sex with men, people having multiple sex partners or people practicing sex without a condom.

• Flu-like symptoms did not always precede the rash and some patients sought medical attention first for lesions in the genital and perianal area.

• In some cases, the lesions are primarily located at these sites, making them difficult to distinguish from syphilis, herpes simplex virus, shingles and other more common infections, according to the Centers for Disease Control and Prevention of the United States.

• Close skin-to-skin contact during sex is the main mode of transmission among men who have sex with men.

• Semen from four patients in Italy collected around the time their symptoms first appeared was positive for monkeypox DNA in three of the cases. It is not yet known if the liquid alone can transmit the infection.

5. Do all infections cause disease?

Maybe not. Retrospective testing of 224 clinical specimens taken in May for screening for sexually transmitted infections found evidence of asymptomatic monkeypox infection in three men. The finding, by researchers at the Institute of Tropical Medicine in Antwerp, Belgium, was reported in a study published July 5 before being peer-reviewed and published. Asymptomatic carriage was previously thought to play a negligible role in the spread of orthopoxviruses, the authors said. The existence of asymptomatic infections indicates that the virus could be transmitted to close contacts in the absence of symptoms, suggesting that identifying and isolating only symptomatic patients will not be enough to contain the outbreak and that vaccination of high-risk individuals is required. Interestingly, one of the asymptomatic men in the study predated the first symptomatic case detected in Belgium by several days, was not linked to other known cases, and had not traveled abroad or attended mass gatherings. The authors said this could suggest the virus was circulating in Belgium before the outbreak was detected.

6. Has the monkeypox virus mutated?

The monkeypox virus could undergo adaptive changes to make it better suited to the human host. Analysis of the genetic sequence of the virus collected from patients in Europe indicates that the current outbreak in non-endemic countries is caused by a strain that likely diverged from the monkeypox virus that sparked a Nigerian outbreak in 2018-19, according to a June 24 study in Natural Medicine. The authors, from Portugal‘s National Institute of Health in Lisbon, identified around 50 genetic changes or differences from the original strain, including several mutations that the authors associate with increased transmissibility. The changes are about 6 to 12 times larger than what scientists would expect based on the observed evolution of orthopoxviruses, they said. The strain belongs to the West African clade, or branch of the evolutionary tree, which generally has a case fatality rate of less than 1%. (That compares to 10% for a second clade called the Congo Basin, which appears on the US government’s list of bioterrorist agents as having the potential to pose a serious threat.)

7. How fast does it spread?

Out of a handful of cases in Europe in early May, more than 7,100 cases, mostly in men, were reported in the region, as well as in the Americas, the Middle East, Asia and Australia in early July. One death has been reported in an immunocompromised person. Experts told a WHO meeting that monkeypox has been circulating undetected in Europe since at least April. Preliminary research estimates that among cases who identify as men who have sex with men, the virus has a reproduction number greater than 1, meaning that more than one new infection is estimated to be from a single case. A UK study found that anonymous sex proved to be a barrier to effective contact tracing, with only 28% of men able to provide the names of recent sexual contacts. This may challenge efforts to stem transmission ahead of LGBTQ pride celebrations taking place in major cities around the world. Data from outbreaks in Canada, Spain, Portugal and the UK suggests that places where men have sex with multiple male partners are contributing to the spread.

8. How is it treated and prevented?

The disease is usually mild and most patients recover within a few weeks. treatment is primarily aimed at relieving symptoms. For the purposes of controlling an outbreak, the CDC says the smallpox vaccine, antivirals, and anti-vaccine immunoglobulin can be used. Smallpox vaccination can be used both before and after exposure and is 85% effective in preventing monkeypox, according to the UK Health Security Agency, which offers the Imvanex smallpox vaccine to close contacts. It lists cidofovir and tecovirimat as antiviral drugs that can be used to control outbreaks. Tecovirimat was approved by the European Medical Association for monkeypox in 2022 but is not yet widely available, according to the WHO. New vaccines based on non-replicating versions of the vaccinia virus have been developed. Bavarian Nordic A/S, the only company with an approved vaccine specifically for monkeypox, will supply the United States with more than 4 million doses of its Jynneos vaccine in 2022 and 2023, according to the Department of Health and Human Services. social. The main way to prevent infection is to isolate patients suspected of having monkeypox and to ensure that healthcare personnel wear appropriate personal protective equipment.

9. Where does monkeypox come from?

The reservoir host or primary vector for monkeypox disease has not yet been identified, although rodents are suspected to play a role in transmission. It was first diagnosed in humans in 1970 in the Democratic Republic of Congo in a 9-year-old boy. Since then, most human cases have occurred in rainforest areas of West and Central Africa. In 2003, the first outbreak outside of Africa occurred in the United States and was linked to animals imported from Ghana to Texas, which then infected prairie dogs. Dozens of cases were recorded during this epidemic.

10. Is monkeypox a pandemic threat?

A meeting of the WHO Emergency Committee on June 23 determined that the event does not currently constitute a public health emergency of international concern. Just over a week later, Hans Kluge, WHO Regional Director for Europe, stepped up his call for governments and civil society to step up their efforts to prevent monkeypox from taking hold. in a larger area. A small number of cases have been reported among household members, heterosexual contacts and non-sexual contacts, as well as among children. Where information is available, nearly 10% of patients are believed to have been hospitalized either for treatment or for isolation purposes, Kluge said.

(Updates to add section 5 on asymptomatic infection, updates to number of cases in section 7.)

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