What Is Monkeypox and How Does It Spread? U.S. Case Confirmed in Maryland

A case of monkeypox has been recorded in the state of Maryland, authorities said this week, marking the country's second such infection so far this year.

The Maryland Department of Health confirmed the infection on Tuesday in a traveler who had recently returned to the U.S. from Nigeria.

The health department said the individual had mild symptoms and was recovering in isolation. It did not recommend any general public precautions, and authorities are working to get in touch with anyone who may have been in contact with the individual.

Monkeypox is a rare disease caused by infection of the virus with the same name. It was first discovered in 1958 in groups of monkeys kept for research, and the first human case was recorded in 1970.

Monkeypox is in the same family of viruses as the smallpox virus, variola. However, it is considered to be a milder disease than smallpox albeit with similar symptoms.

The first symptoms of monkeypox include a fever, headache, muscle aches, swollen lymph nodes, chills and exhaustion, according to the U.S. Centers for Disease Control and Prevention (CDC). Symptoms tend to emerge one to two weeks after infection.

A few days after fever symptoms emerge, patients develop a rash that often starts on the face before spreading to other parts of the body. This rash includes bumps on the skin that then fill with fluid before scabbing and falling off. The illness usually lasts between two and four weeks.

Between humans, monkeypox is thought to be transferred mostly through respiratory droplets via face-to-face contact. It may also be possible to catch it by touching body fluids, rashes, or things the patient has touched. Animals can also transfer it to humans via bite or scratch or if humans handle their raw meat or touch things they have touched.

The CDC states that in Africa monkeypox has been shown to cause death in up to 1 in 10 people who catch it.

Monkeypox is almost always reported in Africa, with the Democratic Republic of Congo reporting more than 1,000 suspected cases a year since 2005. Infections have only occurred in six countries outside of Africa, and outbreaks tend to have been relatively small. CDC data shows there are thought to have been less than 50 cases to have occurred in the U.S. since 1970.

Monkeypox Versus Smallpox

As mentioned, monkeypox is regarded as having similar symptoms to the smallpox disease, but milder.

Smallpox symptoms also start off as a rash with head and body aches that soon develop into a rash that includes liquid-filled bumps, which eventually scab over and fall off. The disease is transferred between people via respiratory droplets or contact with them or things they had touched.

But there are some significant differences between the two diseases. For one, smallpox is considered deadlier.

While monkeypox has been shown to kill up to 1 in 10 people it infects in Africa, the most common form of smallpox has a case fatality rate of about 3 in 10, according to the U.S. Food and Drug Administration (FDA).

Smallpox has also been reported in humans for a lot longer, with cases going back hundreds or even thousands of years, though its exact origin is unknown.

Smallpox outbreaks have also been bigger, and it has been described as one of history's deadliest diseases by the American Museum of Natural History. It's estimated to have killed more than 300 million people since 1900.

Another key difference between smallpox and monkeypox is that the former can be spread through humans only. There is no evidence that animals or insects can spread the virus.

Thanks to a hugely successful international vaccination effort, smallpox was declared eradicated by the World Health Organization (WHO) in 1980.

Monkeypox lesion
A photo purportedly showing monkeypox lesions on someone's hands, taken in June 2003. Monkeypox causes patients to develop a rash. CDC / Getty