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Researchers are keeping a close eye on what appears to be a rapidly developing global outbreak of monkeypox virus. This isn't like previous encounters with the virus. The widespread nature of the outbreak and evidence of frequent human-to-human transmission has researchers questioning whether the virus has .

While it will take some time before that can be known for sure, here's what science does know about monkeypox virus.

Taxonomy

The monkeypox virus is a member of the family Poxviridae and the genus Orthopoxvirus, which includes variola (the virus that causes smallpox), vaccinia (which is used in the smallpox vaccine), and cowpox virus.

Cases

As of Friday, May 20, cases have been confirmed or are under investigation in the U.S. (Massachusetts and New York), U.K., Spain, Portugal, France, Canada, Sweden, and Italy.

The fact that not all the individuals infected traveled to West or Central Africa, where the disease is more common and mainly jumps to people though contact with animals, suggests that the virus may be spreading under the radar.

While this has given epidemiologists pause, there's no proof yet that the virus has changed to become more transmissible.

Much of the transmission so far has occurred among men who have sex with men, but that certainly doesn't mean it's limited to that community.

Transmission

Generally, monkeypox is not easily spread between humans. , human-to-human transmission is thought to primarily occur through large respiratory droplets.

Other means of transmission include direct contact with body fluids or lesions, and indirect contact with lesion material through contaminated clothing or bedding, also known as fomites.

While there's some preliminary evidence of aerosolization, that's not a major route of spread. Thus, spread should be slower than for an airborne virus, contact tracing should be easier, and social distancing should be more effective.

While the reservoir host of monkeypox is still unknown, it's thought that African rodents play a role in transmission.

Incubation

The CDC says the typical incubation period for monkeypox is 7 to 14 days, but can range from 5 to 21 days.

Symptoms

Among the first symptoms to appear are flu-like symptoms, including fever, aches, and fatigue. Monkeypox infection also involves swelling of the lymph nodes.

Then, typically 1 to 3 days later -- though sometimes longer -- a rash develops, according to the CDC. It often starts on the face before spreading to other parts of the body.

Illness typically lasts about 2 to 4 weeks.

Fatality Rate

While the Congo Basin strain of monkeypox is thought to have a fatality rate of 10%, the West African strain -- which was confirmed in the U.K. outbreak -- has a fatality rate of about 1%.

Past U.S. Outbreaks

In 2003, there were 47 confirmed and probable cases of monkeypox in people in the Midwest. All had become ill after coming into contact with pet prairie dogs that had been infected after being housed near animals imported from Ghana.

There were also two travel-related cases in the U.S. in July and November 2021.

Treatments

According to the CDC, there's no proven treatment for monkeypox specifically, but the smallpox vaccine, antivirals, and vaccinia immune globulin can be used.

The (also known as Imvamune or Imvanex) is indicated for monkeypox as well. It's an attenuated, live-virus vaccine incapable of replicating in the human body.

The federal government also reportedly has a stockpile of other smallpox virus vaccines that can be used. The U.S. government stopped its smallpox vaccination program in 1972, but it's thought that people who received the vaccine .

Historically, smallpox outbreaks were contained by ring vaccination, which involved identifying cases quickly, isolating close contacts, and vaccinating all contacts within 4 days of exposure, which usually prevents infection, . "This strategy would likely work for monkeypox, if contacts agreed to be vaxxed," he said.

While there are no proven antivirals specific to monkeypox, cidofovir and brincidofovir may be used. According to the CDC, some in vitro and animal studies of these compounds have shown activity against poxviruses.

Another drug, tecovirimat (Tpoxx), is in an oral and now intravenous form. In the EU, tecovirimat is also indicated for monkeypox. It has been shown in animal studies to be effective in treating orthopoxvirus-induced disease, and human trials involving healthy subjects indicated the drug was safe and well tolerated with only minor side effects, according to the CDC.

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