What is known about simian smallpox?

What is known about simian smallpox?


1. What is simian smallpox?

Also known as monkeypox (simian orthopoxvirus), the disease was first detected in the 1950s, when two outbreaks occurred in monkey colonies used for research. The first human case was reported in 1970 in the Democratic Republic of the Congo (DRC).

Smallpox is endemic in West Africa and is generally rare elsewhere in the world.

This disease, also called smallpox, is often considered a benign form of smallpox. Recall that the World Health Organization (WHO) declared smallpox eradicated worldwide in 1980.

2. What are the symptoms?

Rash can occur in people with smallpox.

Photo: Brian WJ Mahy

Reported symptoms include skin lesions in the mouth and genitals similar to those caused by chickenpox. These symptoms may be preceded or accompanied by fever, night sweats, headache, swollen lymph nodes, and joint or muscle pain.

The incubation period varies from 5 to 21 days. An infected person can be contagious five days before the first symptoms and continues to be infected for the entire time they have skin lesions.

Most patients are not hospitalized, and the symptoms usually go away without treatment.

However, very rare cases of serious complications can occur. For severe infections, there are some experimental antiviral treatments, such as tecovirimat, cidofovir, or brincidofovir.

The mortality rate for this (West African) strain of the disease is 1%. The mortality rate is slightly higher in children and immunocompromised individuals.

3. How many cases?

Test tubes containing virus samples.

The number of cases of simian smallpox is growing rapidly around the world.

Photo: Reuters / DADO RUVIC

The first case of smallpox outside Africa was detected in the United Kingdom on 6 May, according to theWHO. The infected person was returning from a trip to Nigeria.

On May 23, some 200 cases were reported elsewhere than in Africa; on May 30, more than 250 cases.

According to a count of researchers from the Global.health group (New window), as of June 2, 2022, there were about 775 confirmed cases in nearly 30 countries and about 100 suspected cases. No deaths were reported.

The countries with the most confirmed cases are: England (199), Spain (156) and Portugal (138).



Canada has about 60 cases, the vast majority in Quebec. In the province, the number of confirmed cases has gone from 25 to more than double in less than a week.

At this time, we are talking about a probable case when a person has symptoms of the virus and has had contact with a confirmed or probable case or has traveled to an area where a confirmed case has been detected. . People with no epidemiological link but with signs and symptoms associated with the disease are classified as suspicious.

In Africa, 7 of the 54 African countries reported the presence of the disease, and there were about three times more cases of smallpox than usual. According to the African Centers for Disease Control and Prevention, more than 1,400 suspected cases and 63 deaths have been reported in Cameroon, the Central African Republic, the Congo and Nigeria. Less than 50 cases have been confirmed, as screening capacity is limited in these countries.

Genetic sequencing has not been shown to be directly linked to the outbreak outside of Africa, according to health officials. The current outbreak suggests that the virus has spread worldwide without being detected for some time.

4. How does the virus spread?

The disease is usually transmitted from infected animals to humans, but it can also be spread by humans. It can be transmitted through close physical contact with an infected person, clothing or sheets.

However, some questions remain unanswered. For example, it is not known whether infected but asymptomatic people can spread the disease or whether the disease could be transmitted through the air, as is the case with measles or COVID-19. It is believed that air transmission is less common, but not impossible.

Many of the cases involve men who have had sex with other men, but theWHO It is important to remember that simian smallpox is not considered a sexually transmitted disease. The disease would be transmitted due to close contact and not due to the sexual activity itself.

5. Can smallpox be prevented?

The smallpox vaccine is also 85% effective against simian smallpox, and it seems that the immunity conferred by vaccination lasts more than 25 years.

However, routine immunization programs ended in Canada and around the world in the early 1970s.

Large-scale vaccination campaigns are not currently recommended. Several countries, including Canada and the United Kingdom, vaccinate some high-risk individuals, including those who have had close contact with people suspected of being infected.

6. Why so many cases right now?

Health workers take samples.

Thousands of cases have been reported in parts of Africa in recent years.

Photo: Getty Images / Melina Mara

This is the first time that theWHO observes so many cases in so many countries at once, elsewhere than in Africa.

In 2003, a monkeypox epidemic struck the United States. Some 70 cases had been identified; none had led to a death.

However, many scientists are not surprised to see this explosion of cases around the world.

The number of cases of simian smallpox in Africa increases for several years (New window).

From 2005 to 2007, fewer than 800 cases were reported in the DRC. More than 2,800 suspected cases were reported in 2018 and then 3,800 in 2019.

In 2020, there were almost 6,300 cases, including 229 deaths. Cases were also on the rise in neighboring Sudan and the Republic of the Congo. In Nigeria, more than 500 cases have been reported since 2017.

Researchers had, by the way warn in 2010 (New window) that, because a large proportion of the population has never received the smallpox vaccine, the ape strain could spread beyond the Democratic Republic of the Congo.

In fact, the majority of cases in the Republic of the Congo in recent years are young people who have never been vaccinated against smallpox.

In addition, according to the same researchers, animal migration caused by climate change and deforestation fuel human-animal interactions, which facilitates the spread of viruses such as smallpox to humans.

The high number of cases in Africa, combined with more travel since the lifting of restrictions on the COVID-19 pandemic, may have created the ideal conditions for its rapid spread.

According to himWHO, there is still no concrete evidence that the virus has mutated. It should be noted that these orthopoxviruses tend to be fairly stable.

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