Human monkeypox leads to skin irritations with pustules and blisters that eventually burst and then scab over, though they rarely leave scars. The infection is similar to normal pox (smallpox or variola).

The cases registered in the United Kingdom have been reported as the West African strain, which is relatively mild compared to the Central African variant. The illness generally runs its course within three to four weeks. The West African strain is seldom deadly — and when it is, it's mostly in small children.

As a precaution, Robert Koch Institute (RKI) has issued a warning for Germany, urging citizens to be vigilant. 

How are the infections transmitted?

Human-to-human transmission of monkeypox requires close bodily contact. Often, the transmission chain is broken after a small number of individuals are infected. Currently, researchers are intensively trying to ascertain whether transmission occurs through contact between damaged or injured skin and pox secretions.

Monkeypox has an incubation period of seven to 21 days, according to RKI. Beyond skin irritation, head, muscle and backache are common symptoms, and fever, chills and swollen lymph nodes may occur as well.

After the first case was reported in the UK earlier in May, authorities were quickly able to trace the virus' origins as the patient had seemingly contracted the rare infection on a trip to Nigeria.

Tracing the four newly reported cases has been more difficult, however, as none of the men had been to Africa prior to their infection, nor did they have contact with each other.

Health authorities are now feverishly attempting to solve the mystery of how the cases are connected, as monkeypox is not easily transmitted and usually requires close bodily contact in order to be passed from one individual to another.

Transmission through close physical contact

According to British health authorities, the four infected individuals identified as gay or bisexual men. Still, many health experts in the UK have made clear that they have yet to see sufficient evidence to suggest human monkeypox is a sexually transmitted infection.

"Although the current cluster of cases is in men who have sex with men, it is probably too early to make conclusions about the mode of transmission or assume that sexual activity was necessary for transmission, unless we have clear epidemiological data and analysis," said Dr. Michael Skinner, a virology expert at Imperial College London.

Jimmy Whitworth, professor of international public health at the London School of Hygiene and Tropical Medicine (LSHTM) is of a similar opinion: "The most likely mode of spread in this cluster is through close contact: touching skin or bedding, or shared utensils. There is no need to postulate actual sexual transmission through genital or oral secretions."

Still, Susan Hopkins of the UK Health Security Agency (UKHSA) has urged extreme caution, saying: "The UKHSA is advising gay and bisexual men, as well as other communities of men who have sex with men, to look out for unusual rashes or lesions on any part of their body, in particular their genitalia."    

Classic zoonosis

Monkeypox was first detected in humans in 1970, in the Democratic Republic of Congo (DRC). Despite isolated cases of the infection across Central and West African countries since then, the World Health Organization (WHO) says the endemic threat posed by monkeypox is extremely low.

According to Germany's RKI, the virus may be transmitted from animals to humans through "close contact with infected animals as a result of a bite (squirrels, rats, primates), proximity (house pets), contact with animal blood or secretions, ingestion (eating infected monkey meat) or droplet infection." In other words, classic zoonosis, caused either by close contact with, or the eating of, infected animals. 

This article was originally written in German. 
Translation by: Jon Shelton