Within weeks, about 80 new cases of monkeypox were reported in eight European countries, an unprecedented outbreak of a disease rarely found outside Central and West Africa. A small number of additional cases have been reported in the United States, Canada and Australia since Wednesday.
The growing number of cases has raised questions among disease experts about the nature of monkeypox transmission, as many patients have no history of travel to Africa or exposure to an infected person.
“How they initially became infected and why they spread everywhere remains a mystery,” said Dr. Stuart Isaacs, associate professor of medicine at the University of Pennsylvania.
Monkeypox is not easily transmitted from person to person. Experts said that most infections so far have been among people who have been exposed to an infected animal through bites, scratches or preparing meat from wild animals. The most notable outbreak of the disease in the Western Hemisphere occurred in 2003, when pet prairie dogs infected 47 people in the United States
From previous cases of human-to-human transmission, scientists have learned that the virus spreads through the exchange of large respiratory droplets or by direct contact with body fluids, lesions that form during infection, or contaminated items such as clothing or bedding. Experts said monkeypox is not considered a sexually transmitted infection, but can be transmitted during sexual encounters.
Many of the recent cases in Europe are among men who have sex with men, and a Friday warning from the Centers for Disease Control and Prevention indicated that some of the recent cases started with lesions around the anus and genitals.
“I think sexual transmission would be at the top of the list of potential culprits,” said Dr. Grant MacFadden, director of the Biodesign Center for Immunotherapy, Vaccines, and Virotherapy at Arizona State University.
McFadden, Isaacs, and many other experts provided their early ideas about how and why the new outbreak was amplified.
McFadden said the genetic sequence of the monkeypox virus that infected people in Europe appears relatively unusual. This is evidence that human behavior, rather than changes inherent in the virus itself, may be driving the new cases.
“It could just be a simple occasional streak, for example, in the gay community,” McFadden said.
Viruses are often transmitted more easily within tight-knit groups of people. According to Global.health, a group that collects infectious disease data, all recent cases of monkeypox of the sex of which were reported have been male.
“You can imagine that someone had it, and if they were part of a small, intimate group of people, they could spread it between those links,” said Dr. David Evans, a virologist at the University of Alberta.
But this does not explain why cases are geographically spread. Experts also agreed that it’s too early to suggest that monkeypox is only spreading within any one community. It will be important to identify and study the first case of human-to-human transmission to determine how the outbreak began, they said.
Some experts have hypothesized that the easing of international travel restrictions may have contributed to the spread of the disease.
“It seems the virus has always had this potential” to pass from human to human, McFadden said. “It never had a chance in the past – or if it did, it quickly faded away and we would never have seen it as an event. While people are now able to travel all over the world, it is entirely possible that we are actually seeing it for the first time in context. Larger “.
People may be more likely to get monkeypox now than they were in the past
Most people with monkeypox recover completely. In the past, only 1 percent of people infected with the West African strain responsible for the new outbreak died. But a different strain of the virus, the Congo Basin clade, has caused nearly 10 percent of deaths, according to the World Health Organization.
Monkeypox belongs to the smallpox virus family, which includes smallpox. The World Health Organization estimates smallpox vaccines to be 85 percent effective in preventing monkeypox. But the United States stopped vaccinating people against smallpox in 1972, and universal vaccination stopped around 1980, when smallpox was eradicated worldwide.
So people’s immunity to smallpox viruses is generally lower than in past decades.
“We no longer have immunity, so we will continue to see cases emerge — and more of them over time,” said Ann Rimoen, professor of epidemiology at the University of California, Los Angeles Fielding School of Public Health.
Isaac said the low immunity of the population could also explain why Africa has recorded more monkeypox cases in recent years. The Democratic Republic of the Congo reported as many as 18,000 confirmed or suspected cases of monkeypox from 2010 to 2019, but fewer than 10,000 cases between 2000 and 2009. In 2020 alone, the country reported more than 6,000 suspected cases, according to an organization Global Health.
Doctors may have missed some early cases
Several experts have suggested that monkeypox virus may have started spreading in Europe some time before it landed on scientists’ radars.
“Given the geographically dispersed nature of cases across Europe and beyond, this suggests that transmission may have been ongoing for some time,” Dr Hans Kluge, WHO regional director for Europe, said in a statement on Friday.
Isaac said doctors can sometimes miss a case of monkeypox because the rash resembles chickenpox, syphilis, or herpes.
“Most doctors and clinics don’t think about monkeypox,” he said. “Maybe it was brewing over time and no one thought to identify or consider this.”
This is especially likely if the patient has mild illness, McFadden said. So far, that has been the case among most new infections, according to reports from the United States, Belgium, Canada, Germany and Portugal. No recent deaths have been reported.
“If it was particularly mild, maybe someone didn’t really notice much and didn’t think much about what was going on and then spread it among their social group,” Evans said.