According to the World Health Organization website: "Monkeypox is a rare viral zoonosis (a virus transmitted to humans from animals) with symptoms similar to those seen in the past in smallpox patients, although it is clinically less severe".
Initial symptoms of the disease include muscle aches, headache, fever, backache, swollen lymph nodes, exhaustion, and chills. It has been seen to affect humans rarely and some cases have been reported in central and western African countries.
Most patients recover within a few weeks and do not need treatment, but it can cause severe illness in some people.
Both patients are however said to be receiving appropriate care at Royal Infectious University, an expert respiratory infectious disease centre.More news: Ericsson brings 5G to life for United States operators
Nick Phin, deputy director of the National Infection Service at PHE, said that "sporadic cases" of monkeypox have been reported since there was a "large sustained outbreak" of the virus in September 2017 in Nigeria.
Public Health England (PHE) said it was unusual to see two cases in such a short space of time and officials were searching for anyone, including medical staff, who had come into contact with either patient, to offer them health advice.
Monkeypox is related to smallpox, but is less infectious and less deadly.
The unidentified patient had recently been to Nigeria, where they are understood to have picked up the disease.
Person-to-person transmission can occur if somebody used the bedding or towel of an infected person, comes into direct contact with a skin lesion, or is exposed to droplets from a patient coughing or sneezing.More news: Liverpool need Bayern's mentality to win titles - Shaqiri
The monkeypox virus was first discovered in 1958 when outbreaks of a pox-like disease occurred in monkeys kept for research, says the United Kingdom government website's infectious diseases portal.
Mike Beadsworth, clinical director of the Tropical and Infectious Diseases Unit at the Liverpool hospital, said in a statement that there was "currently no risk to other staff, patients or visitors", and urged people to continue to only visit emergency rooms if their cases are serious. We'll collaborate with Public Health England to investigate this case.
A rash can also develop, which usually starts on the face and spreads, forming a scab which falls off.
The recent outbreak in Nigeria - the first since 1978 - resulted in 172 suspected and 61 confirmed cases (across 14 states) between September and December 2017.
Symptoms usually appear about two weeks after a person is exposed to monkeypox.More news: Cuomo-Nixon showdown in NY governor's race goes to voters