Two different variants of smallpox have been found in the United States, exacerbating the mystery of the epidemic

According to new sequencing data from the Centers for Disease Control and Prevention, at least two genetically different monkeys are endemic in the United States.

Although the CDC has not listed all 22 confirmed cases in the United States, two of them have been found to be genetically similar to a human infection in Texas that went to Nigeria in 2021. Both have recently traveled to Africa, including a woman from Virginia and a man from Florida.

The remaining consistent U.S. cases are similar to the genetic code of affairs in Europe, with a Maryland resident who traveled to Nigeria in 2021 to be infected.

“Although they are similar to each other, their genetic analysis shows that they are not related to each other,” Jennifer McQueiston, deputy director of the CDC’s Highly Dangerous Pathogens and Pathology Division, said at a press briefing on Friday about the two options. .

According to Mackiston and other disease experts, this new information shows that cases in the United States are caused by not one, but two epidemics, making it difficult to understand their origin.

“Apparently, in the last two years, there have been at least two other cases in which the monkey smallpox virus has spread to humans from the animal that caught it in Nigeria, and the virus has begun to spread from person to person through close contact. Possibly intimate or sexual contact,” McQuiston said.

This possibility, in turn, raises questions about how long monkeys have been spreading outside Africa and how contagious the virus is.

“It’s like getting used to a new TV series and we don’t know which episode we’re in,” said Anne Rimoin, an epidemiology professor at UCLA School of Public Health. “We’re starting to get a little bit of origin history now.”

Did the monkey’s smallpox spread unnoticed?

According to, a group that collects data on infectious diseases, about 900 cases of smallpox have been reported outside Africa since the beginning of May. The largest epidemic in the Western Hemisphere in the United States in 2003 was 47 cases. These people were sick with pets and dogs; Human-to-human transmission has not been documented.

Experts are weighing various possible explanations for the rapid growth of current epidemics. These several events may have allowed the virus to spread. Or apes may have evolved to improve human-to-human transmission. The third hypothesis is that the virus may have been spreading unnoticed for some time.

WHO Director-General Tedros Adhanom Gebreyus suggested a third option this week.

“It simply came to our notice then [the variants] now, because we’re looking so hard, ”said Andrew Reed, a professor at Pennsylvania State University who has studied the evolution of infectious diseases.

But McQueen said he would not miss the previous large-scale epidemic.

“Of course, there may be cases of monkey disease on the radar in the United States in the past, but it’s not a big one,” he said.

“Many genes to play”

As for the idea that the virus has become more contagious, Reed noted that ape-smallpox is spreading more effectively between close contacts than scientists have previously observed.

Monkeypox is a DNA virus that does not mutate as quickly as RNA viruses, such as the coronavirus. However, Red noted that DNA viruses have long genomes: the smallpox genome is seven times larger than the coronavirus.

“The fact that he has so many genes to play with means that different things can happen,” he said.

Stephen Morse, a professor of epidemiology at Columbia University, said it remains to be seen whether one option will spread more easily than the other.

“It would be important to know if a particular option has a longer human-to-human transmission cycle,” he said.

But Rimuin said it was too early to tell if monkeys had evolved in any way.

The scale of the epidemic, he said, “does not mean the virus itself has changed.”

More infections make it harder to catch the virus

Experts are optimistic that the U.S. epidemic can still be contained, but they fear an ongoing outbreak.

“I’m very worried about whether it’s very common in these people,” Reed said. “As with Covid, the potential to become widespread and contagious over time would be very unfortunate.”

The more widespread the cases, the harder it is to catch them, but that doesn’t mean “it’s impossible,” Rimoin said.

Experts know how to stop monkey smallpox: screening people with symptoms, isolating infected patients and vaccinating their loved ones.

“I don’t believe these two exist [variants] Now rotation complicates control measures, “Reed said.” Let’s stop evolution by getting rid of these things now. “

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