A patient in England has been diagnosed with a rare case of monkeypox, Public Health England (PHE) has confirmed.

The rare viral infection is similar to smallpox, and though it is milder, it can be fatal. 

The individual, who has not been named, is believed to have contracted the infection whilst visiting Nigeria. On returning to the UK, they were staying in the southwest of England when they fell ill, after which they were admitted to a specialist high consequence infectious disease center at Guy’s and St Thomas’ NHS Foundation Trust in London. The health authority says it has begun measures to ensure the virus doesn't spread to others.

"As a precautionary measure, PHE experts are working closely with NHS colleagues to implement rapid infection control procedures, including contacting people who might have been in close contact with the individual to provide information and health advice," PHE said in a statement.

However, they are not overly concerned about a potential outbreak as it is not easily passed between humans. "Monkeypox does not spread easily between people and the overall risk to the general public is very low," Dr Meera Chand, Consultant Microbiologist at PHE, said.

The infection is usually mild and people usually get better without any treatment. However, some people can develop more serious symptoms, with between one and 10 percent of patients dying of the disease during outbreaks, according to the World Health Organization. 

Symptoms are similar to smallpox, though milder. Initial signs include fever, headache, muscle aches, backache, swollen lymph nodes, chills, and exhaustion. After this a rash may develop, likely beginning on the face before spreading to other parts of the body. Most patients will recover from the illness within a few weeks. 

Monkeypox was first discovered in 1958 after several outbreaks in monkey populations kept for research in Africa, according to the Centers for Disease Control and Prevention (CDC). The first human case was recorded in the Democratic Republic of Congo (DRC) in 1970. The human version is largely transmitted from animals to humans, known as a zoonotic disease, rather than human to human.

The vast majority of cases have taken place in the DRC since, where over a thousand a year have occurred since 1970, the CDC reports. A few smaller outbreaks have taken place across central and western Africa. Only three countries outside of Africa have had cases of the disease; the US had the largest outbreak with 37 confirmed cases in 2003. It was caused by a shipment of animals from Ghana that included some infected with the disease.

This isn't the first time the infection has been seen in the UK either, with three cases taking place in 2018 after a patient brought the infection back with them, having been a resident of Nigeria.