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The symptoms and causes of monkeypox infections, now diagnosed in more than 20,000 people

Widespread cases prompted the World Health Organization to declare monkeypox a public health emergency last week.

More than 20,000 cases of monkeypox have been confirmed across 71 countries where the virus isn't historically found.

The European Union had recorded 11,000 cases as of Thursday, including more than 3,700 cases in Spain and nearly 2,500 in Germany. The United Kingdom has documented around 2,500 cases as of Friday, while the U.S. total is up to 4,900.

The World Health Organization declared monkeypox a public health emergency of international concern last week. WHO Director-General Tedros Adhanom Ghebreyesus said the virus's spread poses a moderate risk globally and a high risk in Europe.

"We have an outbreak that has spread around the world rapidly, through new modes of transmission, about which we understand too little," Tedros said. "For all of these reasons, I have decided that the global monkeypox outbreak represents a public health emergency of international concern."

Five people in Africa have died of monkeypox this year. No deaths outside Africa have been linked to the current outbreak.

Most of the recent cases are among men who have sex with men, especially those with multiple partners.

How dangerous is monkeypox?

Monkeypox belongs to the family of poxviruses, which includes smallpox. The disease got its name after scientists discovered it among laboratory monkeys in 1958. The first monkeypox case in a human was diagnosed in 1970.

Since then, most infections have been concentrated in the Democratic Republic of the Congo and Nigeria. The DRC reports thousands of cases annually and Nigeria has reported hundreds of confirmed or suspected cases since 2017.

The last time the Western Hemisphere saw a relatively large monkeypox outbreak was in 2003, when the U.S. identified 47 cases. Those patients had been in contact with infected pet prairie dogs, and no people died.

The type of monkeypox identified globally in the current outbreak, known as the West African strain, tends to produce milder disease than the other common branch, the Congo Basin strain.

Around 1% of people who have contracted the West African strain in the past have died, compared with up to 10% of people who contract the Congo Basin strain, according to the WHO.

What are the symptoms of monkeypox?

Monkeypox symptoms can develop up to 21 days after someone is infected, though usually appear within one to two weeks. Most people recover after two to four weeks.

During the current outbreak, many people have developed a rash around the genital and anal region, on the face, or on the palms of hands and soles of feet. Some people have also seen lesions inside the mouth, throat, vagina and anus.

Monkeypox rashes can range from one or two lesions to several thousand, according to the WHO. The rash can look similar to chickenpox, syphilis or herpes. It typically progress from red areas to small bumps on the skin. Those bumps can then turn into blisters that may fill with whitish fluid.

People may also develop flu-like symptoms such as fever, swollen lymph nodes, headaches, muscle aches, back pain and fatigue.

How do you get monkeypox?

Monkeypox is primarily spreading through close physical contact, including hugging, kissing or sex. People can be exposed to monkeypox during these activities through contact with bodily fluids or lesions.

The virus can also spread through respiratory droplets and contaminated items like clothing or bedding.

Historically, some people have contracted monkeypox from animals, either through bites or scratches or while preparing meat from wild game.

People with monkeypox are most infectious when they have active lesions. The WHO recommends that people with diagnosed infections isolate "until all their lesions have crusted over, the scabs have fallen off and a new layer of skin has formed underneath."

What treatments are available?

Monkeypox lesions can be extremely painful, so some people require prescription medication or even hospital care to help manage the discomfort.

Doctors can also treat symptoms with an antiviral drug called TPOXX, which is authorized for use against smallpox.

The U.S. has 1.7 million doses of TPOXX in its Strategic National Stockpile, the Department of Health and Human Services said Thursday. But the drug's use is still limited.

"There are substantial barriers to making TPOXX widely available for monkeypox, usually requiring a significant amount of paperwork," White House Covid-19 Response Coordinator Ashish Jha said last week.

Which vaccine is used for monkeypox?

The Food and Drug Administration approved a two-dose vaccine called Jynneos in 2019 for use against monkeypox and smallpox. The vaccine may prevent monkeypox if given within four days of exposure, or ease symptoms if given within 14 days. Research suggests the Jynneos shot can reduce the risk of infection by about 85%.

HHS said Thursday that the U.S. had distributed 338,000 Jynneos doses. An additional 786,000 doses became available on Friday.

The U.S. also has more than 100 million doses of an older-generation smallpox vaccine called ACAM2000 in the national stockpile. But that vaccine isn't being distributed to the public, since it can't be given to immunocompromised people.

Jha said Monday that the U.S. has "procured more vaccines than any other country in the world."