What we know about the current monkeypox outbreak

A man in Massachusetts tested positive for the rare virus earlier this month.

This 2003 electron microscope image made available by the Centers for Disease Control and Prevention shows a monkeypox virion, obtained from a sample associated with the 2003 prairie dog outbreak. Cynthia S. Goldsmith, Russell Regner/CDC via AP

Monkeypox, a rare virus normally found only in Africa, is now at the forefront of many peoples’ minds after cases appeared in Massachusetts, Canada, and parts of Europe. But what is monkeypox, and how concerned should residents be?

The virus was initially discovered in 1958 when two colonies of monkeys kept for research were diagnosed. The first human case was recorded in 1970 in the Democratic Republic of Congo, according to the Centers for Disease Control and Prevention. Since then, it has largely been contained to central and western Africa. The virus is closely related to the variola virus, which causes smallpox. African rodents and non-human primates like monkeys can infect humans. 

On May 18, a man in Massachusetts who had traveled from Canada tested positive for the virus. While the Massachusetts man remains the only confirmed case in the country, there are four suspected cases in the United States, the CDC said Monday.


The sudden appearance of a rare virus could be alarming after more than two years of a global pandemic. 

“I think people are a little bit more on edge because of COVID,” said Phyllis Kanki, an Immunology and Infectious Diseases professor at the Harvard School of Public Health. “I think there’s concern because this is something that hasn’t been seen for many years in the U.S. and now it’s popping up in a lot of countries. That dynamic, the time course and the reports from different countries is a little troubling.”

However, Kanki said, the personal risk remains low for most people. Transmission between humans usually occurs through large respiratory droplets, and prolonged face-to-face contact is required, according to the CDC. Transmission can also come from direct contact with body fluids or lesion material, or indirect contact with lesion material, such as through contaminated clothing or linens. 

A notable fraction of cases globally are occurring in people who self-identify as men who have sex with men, according to the CDC. However, John Brooks, chief medical officer for the CDC’s Division of HIV/AIDS Prevention, said Monday that the risk of exposure to monkeypox is not exclusive to the gay and bisexual community, CNN reported


A monkeypox infection can generally be divided into two phases, according to the World Health Organization. The invasion period normally lasts around five days. Symptoms include fever, intense headache, swelling of the lymph nodes, back pain, muscle aches and intense lack of energy. Lymph node swelling is a distinct symptom for monkeypox compared to other diseases that may initially appear similar like chickenpox, measles, or smallpox. 

The second phase usually begins one to three days after a fever. Rashes appear concentrated on extremities and the face. Recent cases have also been reported to include rashes and lesions in the genital and perianal area, Brooks told CNN. The rash evolves quickly into lesions filled with yellow fluid. The number of lesions can vary from a couple to several thousands, according to the WHO. 

Officials are now in the process of releasing a two-dose vaccine approved in the U.S. for use against smallpox and monkeypox in high risk adults aged 18 and older, Reuters reported. There are more than 1,000 doses of the vaccine in a national stockpile. People who’ve had contact with known monkeypox patients and healthcare workers will be prioritized. 

The current strain seen in the United States, believed to come from west Africa, is not quite as dangerous as other strains seen in central Africa, Kanki said. Nigeria, where Kanki frequently works, has been home to a large monkeypox outbreak and other cases that have periodically surfaced, she said. 


“Historically it hasn’t been something that they’ve worried about people spreading from close contact. Of course you could get it that way…but it isn’t something that’s considered easily transmitted,” Kanki said. 

The case fatality ratio of monkeypox has historically ranged from 0 to 11 percent in the general population, according to the WHO. It has been higher among young children. In recent years, the case fatality ratio has been around 3 to 6 percent.

This is not the first outbreak in the United States. In 2003, Illinois, Indiana, Kansas, Missouri, Ohio, and Wisconsin reported 47 confirmed and probable cases, according to the CDC. These people caught the virus from pet prairie dogs. The prairie dogs were infected after being housed near imported small mammals from Ghana.

The current outbreak was described as a “random event,” that could be tied to two raves held in Spain and Belgium according to David Heymann, who formerly led WHO’s emergencies department, in an interview with the Associated Press. 

While not explicitly transmitted sexually, close contact during sex can cause lesions to burst and amplify transmission. 

“That’s unusual and hasn’t been recognized before with monkeypox,” Kanki said. “That’s the aspect that has people a little bit concerned, because it’s so different. It remains to be seen if that really bears out or if it’s something unusual that will still die away like other outbreaks in the past.”


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