Over 40 suspected cases of monkeypox have been detected in England, Spain and Portugal and one case in the United States of America. But health officials in Europe haven't traced the source of the virus yet.

"This is rare and unusual. UK Health Security Agency is rapidly investigating the source of these infections because the evidence suggests that there may be transmission of the monkeypox virus in the community, spread by close contact," said Dr Susan Hopkins, chief medical adviser of UKHSA, on May 16, 2022.

The disease, which is most common in central and west Africa, typically kills up to a tenth of the people infected with most deaths occurring in younger age groups, according to the World Health Organization.

Here's a lowdown on the epidemiology, symptoms and treatment of the disease.

What is Monkeypox?

Monkeypox is a sylvatic zoonosis and a rare disease that belongs to the Orthopoxvirus genus, according to the WHO. This particular species also includes variola virus (which causes smallpox), vaccinia virus (used in the smallpox vaccine), and cowpox virus.

"Monkeypox virus is very similar to the virus that used to cause smallpox," Dr Umang Agrawal, Infectious Diseases Consultant at Mumbai's PD Hinduja Hospital, told FactChecker. "There was another virus that was used to make a vaccine against smallpox known as variola. When the patients used to be vaccinated for smallpox regularly, the vaccine used to provide protection against monkeypox as well since both viruses are similar. But ever since the smallpox vaccination has died down, the incidence of monkeypox has increased."

The virus was first discovered in 1958 when two outbreaks of a pox-like disease occurred in colonies of monkeys kept for research, according to the Centers for Disease Control and Prevention (CDC). The first human case of monkeypox was recorded in 1970 in the Democratic Republic of the Congo (DRC) where efforts were being made to eliminate smallpox.

It's not unusual to have outbreaks this way since, generally, the transmission is through rodents such as squirrels, rats, etc, said the infectious disease expert. "The generally known way of transmission is through close contact with wild animals from the African region. There were outbreaks in the USA in 2003 when they localised the causes of the outbreak to be a Prairie dog," said Dr Agrawal.

There are two clades or groups of monkeypox virus: the West African clade and Congo Basin (Central African) clade, according to the WHO. While the West African type could lead to severe illness in some individuals, the case fatality ratio is reported to be only around 1%. Whereas, the Congo Basin group's fatality ratio could be as high as 10%.

Children are at higher risk of catching the virus and if it infects women during pregnancy, it may lead to complications, congenital monkeypox or stillbirth.

Symptoms of Monkeypox

Monkeypox can be transmitted by droplet exposure through exhaled large droplets and by contact with infected skin lesions. Symptoms are usually similar but milder than smallpox and the lesions can be very itchy or painful. Fever, headache, muscle ache and exhaustion are classic symptoms. While monkeypox causes lymph nodes to swell, smallpox does not, according to the CDC.

The incubation period of monkeypox is usually from one to two weeks but can range from 5 to 21 days as well. The illness generally lasts for 2−4 weeks.

In Africa, monkeypox has been shown to cause death in as many as 1 in 10 persons who contract the disease, as per the CDC.

Monkeypox does not entirely come from monkeys. "Monkeys are only incidental hosts, they are not reservoir hosts," said Dr Agrawal. Reservoir hosts harbour the virus without manifesting any symptoms. So, if the rodent bites a human or a monkey, that particular monkey becomes an incidental host. So monkeys can transmit the virus if they are infected with it, he explained.

Is Sexual Transmission Possible?

Health officials have reported that the virus could be spreading via sexual contact. However, this has never occurred before, they say. "What is even more bizarre is finding cases that appear to have acquired the infection via sexual contact," tweeted Mateo Prochazka, Infectious Disease epidemiologist at the UKHSA. "This is a novel route of transmission that will have implications for outbreak response and control."

Further, Dr Hopkins advised gay and bisexual men to be alert and notice any unusual rashes or lesions on any part of their body, especially their genitalia, and to contact a sexual health service if they have concerns.

"The evolving theory is that it might be sexually transmitted. However, we do not have enough data to conclusively say that. If you look at the previous cases from the early 2000s and in 2018 the majority of patients have a history of travel from Nigeria. But it is difficult to say why it is spreading at a fast rate," said Dr Agrawal.

How Can it be Treated?

While the world has seldom heard of this rare disease, it has been significantly increasing in the Democratic Republic of Congo in Central Africa. The number of cases increased 10-fold between 2010 and 2019, according to a study published in February 2022. In 2020, there were nearly 4,600 suspected cases in the country, mentioned the study.

Currently, there is no approved treatment for this disease and is generally controlled by smallpox vaccine and antivirals. The CDC recommends a smallpox vaccination within two weeks of exposure, ideally within four days, for exposed health care workers and household contacts of confirmed cases.

"Most patients recover simultaneously. It is a viral illness that goes away by itself," said Dr Agrawal. However, clinical studies have shown that Cidofovir can be used to control an outbreak. According to the CDC, data is not available on the effectiveness of Cidofovir and Brincidofovir in treating human cases of monkeypox, however, both have proven activity against poxviruses in in vitro and animal studies.