What we know about the growing cases of monkeypox worldwide

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More and more new cases of monkeypox have been detected around the world, with dozens reported in the UK alone. The increase came after preliminary evidence showed an unknown transmission of the monkeypox virus among the country’s population, according to the UK’s Health Agency (UKHSA). It is believed that monkeypox originated from rodents in Central and West Africa, and it has repeatedly been passed on to humans. Cases outside of Africa are rare and have so far been tracked by infected travelers or imported animals.

On May 7, there were reports that a man who came to the UK from Nigeria had contracted monkeypox. A week later, authorities reported two additional cases in London that apparently were not related to the first. At least four people recently diagnosed as having the disease also had no known contact with the three previous cases – indicating unknown chains of infection in the population.

According to the World Health Organization, everyone is infected in the UK infected with West African virus, a version that tends to be mild and usually goes untreated. The infection starts with fever, headache, limb pain and fatigue. As a rule, after one or three days there is a rash, as well as blisters and pustules resembling smallpox, which eventually become crusty.

“It’s an evolving story,” said Anne Rimouine, a professor of epidemiology at the University of California, Fielding School of Public Health in Los Angeles. Rimouine, who has studied monkeypox in the Democratic Republic of Congo for many years, has many questions: at what point in the disease are people who have been infected? Are these really new cases or older ones that have just been discovered? How many of their primary cases are infections that can be traced through contact with animals? How many of them are secondary, or human-to-human, cases? What are the travel stories of infected people? Are there any connections between these cases? “I think it’s too early to make any final statements,” Rimoine said.

All reported infections include a mild version

Many of those infected in the UK are men who have sex with men and contracted the disease in London, according to UKHSA. Some experts believe that transmission can occur in this community, but can also spread in close contact with others, including household members or health professionals, for example. The virus is spread by droplets from the nose or mouth. It can also be transmitted through body fluids, such as pustules, as well as through objects that have come in contact with them. However, most experts say close contact is necessary for infection.

The cluster of cases in the UK is rare and unusual, says Susan Hopkins, UKHSA’s chief medical adviser. The agency is currently tracking the contacts of those infected. Although data from the Democratic Republic of the Congo in the early 1980s and mid-2010s show that effective breeding numbers at the time were 0.3 and 0.6, respectively, meaning that each infected person transmitted the virus on average to less than one person in these populations. there is growing evidence that it can continue to spread from person to person under certain conditions. For unknown reasons, the number of infections and outbreaks is significantly increasing, so monkeypox is considered a potential global threat.

As the situation is still evolving, experts did not immediately express concern about widespread international outbreaks. “I’m not very worried” about the possibility of a larger epidemic in Europe or North America, says Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine. Historically, the virus has been mainly transmitted from animals to humans, and human-to-human transmission usually requires close or intimate contact. “For example, it’s not as transmitted as COVID, and it’s not even as transmitted as smallpox,” Hotez says.

The bigger problem, he said, is that the virus has spread from animals – possibly rodents – in the Democratic Republic of Congo, Nigeria and West Africa. “If you look at some of our most serious threats of infectious diseases – or [they are] Ebola or Nipa or coronaviruses like [those that cause] SARS and COVID-19, and now monkeypox, are disproportionately zoonotic diseases, diseases that are transmitted from animals to humans, ”adds Hotez.

The proportion of infected people who die from monkeypox is unclear because the data is poor. Known risk groups are people with weakened immune systems and children, and infection during pregnancy can lead to miscarriage. Some sources point to the virus in the Congo Basin mortality of 10 percent or morealthough recent studies show mortality below 5 percent. In contrast, almost all persons infected with the West African version survive. Only a few people died during the largest known outbreak that began in Nigeria in 2017, and at least four of them had weakened immune systems.

There is currently no specific cure for monkeypox itself except antiviral drugs cidofovir, brintsidofovir and tecovirimate can be used. (The latter two are approved for the treatment of smallpox in the United States) Healthcare professionals treat symptoms and try to prevent additional bacterial infections that can sometimes cause problems during such viral illnesses. At the earliest stage of the monkeypox disease, the disease can be alleviated by administering a vaccine against both monkeypox and smallpox or an antibody preparation derived from vaccinated individuals. The United States recently ordered millions of doses of the vaccine to be produced in 2023 and 2024.

Smallpox in monkeys is becoming more common

The number of cases in the UK along with evidence of the constant transmission of people outside Africa suggests that the virus is changing its behavior. A study by Rimouine and her colleagues found a number of cases in the Democratic Republic of Congo can increase 20 times between the 1980s and mid-2000s. And the virus has re-emerged in several West African countries over the years: in Nigeria, for example, since 2017 there have been more than 550 suspicious cases, of which more than 240 have been confirmed, including eight deaths.

It remains a mystery why more people in Africa are now infected with the virus. Factors that have contributed to the recent epidemics of Ebola, which has infected several thousand people in West Africa and the Democratic Republic of the Congo, may play a role. Experts believe that factors such as population growth and the increase in settlements near forests, as well as increased interaction with potentially infected animals contribute to the transmission of animal viruses to humans. At the same time, viruses are generally spreading faster due to higher population density, better infrastructure and more travel, which could lead to international outbreaks.

The spread of monkeypox in West Africa may also indicate that the virus has appeared in a new animal reservoir. The virus can infect a number of animals, including many species of rodents, monkeys, pigs and anteaters. Infected animals transmit it relatively easily to other types of animals and humans – which is what happened during the first outbreak outside Africa. In 2003, the virus entered the United States along with African rodents, which in turn infected meadow dogs that were sold as pets. There are dozens of people in the country contracted smallpox in monkeys during this outbreak.

Along the path of smallpox

The factor that is considered to be the most important in the current course of monkeypox cases is that the coverage of smallpox vaccination worldwide is declining. Smallpox vaccination reduces the risk of smallpox in monkeys by about 85 percent. However, since the end of the smallpox vaccination campaign, the proportion of unvaccinated people has been steadily rising, making it easier for people to become infected with monkeypox. Thus, the proportion of human-to-human transmission among all infections increased from about one-third in the 1980s to three-quarters in 2007. Another factor that indicates a decrease in the number of vaccinations is that the average age of those infected with monkeypox has increased with the amount of time since the end of the smallpox vaccination campaign.

Experts in Africa warn that monkeypox could turn from a regionally prevalent zoonosis into a globally relevant infectious disease. The virus can fill environmental and immunological the niche was once occupied by the smallpox viruswrote Malachi Ifeani Okeke of the American University of Nigeria and his colleagues in a 2020 article.

“Currently, there is no global system to combat the spread of monkeypox,” said Nigerian virologist Oewale Tomori. in an interview published in “Conversation” last year. But it is unlikely that the current outbreak will be an epidemic in the UK. According to UKHSA, the risk to the population is still low. The agency is now looking for additional cases and is working with partners internationally to find out if there are similar outbreaks of monkeypox in other countries.

“Once we find the cases, we’re going to have to do a really thorough investigation of the cases and track the contacts, and then also do some sequencing to really disperse how the virus has spread,” Rimuan says. The virus may have been circulating for some time before health authorities noticed. “If you shine a flashlight in the dark,” she says, “you’ll see something.”

Until scientists understand how the virus is transmitted, Rimwin adds: “We must continue what we already know, but be modest – and remember that these viruses are always able to change and evolve.”

A version of this article originally appeared in Spectrum of science and was reproduced with permission.

What we know about the growing cases of monkeypox worldwide

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