Scientists are puzzled about an unusual outbreak of monkeypox, a rare viral infection typically limited to Africa, spreading across Europe and the Americas.
The WHO says many cases have been in people identifying as gay, bisexual or men who have sex with men, but that the virus spreads through close contact regardless of sexual orientation.
In an interview with the Associated Press, Dr David Heymann, who formerly headed WHO’s emergencies department, said the leading theory to explain the recent outbreak of the disease was sexual transmission among gay and bisexual men at two rave parties held in Spain and Belgium.
“We know monkeypox can spread when there is close contact with the lesions of someone who is infected, and it looks like sexual contact has now amplified that transmission,” Heymann said.
That marks a significant departure from the disease’s typical pattern of spread in central and western Africa, where people are mainly infected by animals like wild rodents and primates and outbreaks have not spilled across borders.
Heymann chaired an urgent meeting of WHO’s advisory group on infectious disease threats on Friday to assess the ongoing epidemic and said there was no evidence to suggest that monkeypox might have mutated into a more infectious form.
Monkeypox has not previously been documented to have spread through sex, but can be transmitted through close contact with infected people, their clothing, or bedsheets.
How did this outbreak start?
The UK Health Security Agency (UKHSA) was the first health authority in Europe to publicly report a case of monkeypox on May 7, in a person who had recently flown into the UK from Nigeria.
On Monday, the agency reported 36 new cases, bringing the country’s total to 56. The UKHSA has recommended particularly looking out for lesions on genitalia.
Authorities in Spain and Portugal said their cases were in young men who mostly had sex with other men and that those cases were picked up when the men turned up with lesions at sexual health clinics.
But on Sunday, the Joint United Nations Programme on HIV/AIDS (UNAIDS) voiced concern that the focus on the gay and bisexual community could reinforce homophobic and racist stereotypes, and emphasised that the disease could affect anyone.
What are the symptoms of monkeypox?
Monkeypox is a relative of smallpox, a disease that was eradicated in 1980, but is less transmissible, causes milder symptoms and is less deadly.
The illness typically lasts for two to four weeks and symptoms can appear anywhere from five to 21 days after infection.
Monkeypox symptoms usually begin with a mix of fever, headaches, muscle aches, backache, chills, exhaustion, and swollen lymph nodes.
This latter symptom is typically what helps doctors distinguish monkeypox from chickenpox or smallpox, according to the WHO.
Once you have a fever, the key feature of monkeypox, a nasty rash, tends to develop one to three days later, often starting on the face and then spreading to other parts of the body.
The number of lesions may range from a few to thousands.
The lesions will go through a painful ripening process, from macules (flat lesions) to papules (raised lesions), vesicles (fluid-filled lesions), then pustules (pus-filled lesions) and then finally scabs (crusty lesions) before eventually falling off.
Why is it called monkeypox?
Monkeypox virus belongs to the Orthopoxvirus genus in the family Poxviridae. It was first discovered in 1958 when two outbreaks of a pox-like disease occurred in lab monkeys kept for research, hence the name.
But monkeys might not be the ones to blame for outbreaks, and the natural reservoir of monkeypox remains unknown, though the WHO says rodents are the most likely.
“In Africa, evidence of monkeypox virus infection has been found in many animals including rope squirrels, tree squirrels, Gambian poached rats, dormice, different species of monkeys,” says the UN health agency.
Where is monkeypox typically found?
Human monkeypox primarily causes outbreaks in the tropical rainforest regions of Central and West Africa and is not typically seen in Europe.
The Democratic Republic of the Congo (DRC) had the first recorded human case of monkeypox in 1970.
The first outbreak of monkeypox reported outside of Africa was linked to the importation of infected mammals in 2003 in the United States, according to the US Centers for Disease Control and Prevention (CDC).
More recently, in 2018 and 2019, two travellers from the United Kingdom, one from Israel, and one from Singapore, all with travel history in Nigeria, were diagnosed with monkeypox following a large outbreak there, according to Europe’s own health agency, the European Centre for Disease Prevention and Control (ECDC),
How do you catch monkeypox?
You can catch the virus from the bite or scratch of an infected animal, by eating bush meat, being in direct contact with an infected human or touching contaminated bedding or clothing.
The virus enters the body through skin lesions, the respiratory tract, or the mucous membranes (the eyes, nose, or mouth).
Human-to-human transmission is thought to occur primarily through large respiratory droplets, which generally cannot travel more than a few feet, so prolonged face-to-face contact would be needed.
Some British experts commenting on the recent UK outbreak said it was soon to conclude that monkeypox had spread through sexual contact, but that it was a possibility.
“The recent cases suggest a potentially novel means of spread,” said Neil Mabbott, a disease expert at the University of Edinburgh, adding that related viruses were known to spread via sex.
Keith Neal, an infectious diseases expert at the University of Nottingham, said the transmission might not have occurred through sexual activity but just “the close contact associated with sexual intercourse”.
The US Centres for Disease Control and Prevention (CDC) stressed in a statement that “anyone, regardless of sexual orientation, can spread monkeypox through contact with body fluids, monkeypox sores, or shared items (such as clothing and bedding) that have been contaminated”.
Should I be worried?
Health authorities say monkeypox is usually a mild illness and most people recover within a few weeks.
“Most of the current cases have presented with mild disease symptoms, and for the broader population, the likelihood of spread is very low,” the ECDC’s director, Andrea Ammon, said on Monday.
“However, the likelihood of further spread of the virus through close contact, for example during sexual activities among persons with multiple sexual partners, is considered to be high”.
The patients infected in England contracted the West African clade of the virus, which health officials say is mild compared to the Central African clade and has a case fatality ratio of around 1 per cent.
Genome sequence from a swab sample from a confirmed case in Portugal indicated a close match of the virus to that of the 2018-2019 outbreak of cases exported from Nigeria to the United Kingdom, Israel and Singapore.
Heymann, the former head of the WHO’s emergencies department, said that the disease was unlikely to trigger widespread transmission.
“This is not COVID,” he said. “We need to slow it down, but it does not spread in the air and we have vaccines to protect against it.”
Although its symptoms are milder than those of smallpox, monkeypox has been shown to cause death in as many as 10 per cent of patients infected with the Congo Basin clade, compared to about 30 per cent for smallpox, according to WHO data.
Mortality is higher among children and young adults, and immunocompromised individuals are especially at risk of severe disease.
Monkeypox during pregnancy may also lead to complications, congenital monkeypox, or stillbirth, according to the WHO.
Treatment and prevention
Monkeypox usually goes away on its own, but an oral antiviral drug called Tecovirimat was approved earlier this year in the European Union to treat smallpox, monkeypox and cowpox and it can limit the spread of the virus and the severity of the infection.
Vaccination against smallpox is believed to be highly effective in preventing monkeypox, but because smallpox was declared eradicated more than 40 years ago, younger populations “no longer benefit from the protection afforded by prior smallpox vaccination programmes,” says the WHO.
The ECDC recommended all suspected cases be isolated and that high-risk contacts be offered a smallpox vaccine.
The UK is offering high-risk contacts the smallpox vaccine and recommending anyone who might be infected to isolate until they recover.
The US has 1,000 doses of a vaccine approved for the prevention of monkeypox and smallpox, plus more than 100 million doses of an older-generation smallpox vaccine in a government stockpile, officials said.
A newer vaccine developed by Bavarian Nordic for the prevention of both smallpox and monkeypox has been approved in the European Union, the United States, and Canada (under the trade names Imvanex, Jynneos and Imvamune), but it’s not yet widely available.
Common household disinfectants can kill the monkeypox virus, says the CDC.
Self-isolation and self-monitoring are key
Any patient with suspected monkeypox should be investigated and – if confirmed – isolated “until their lesions have crusted, the scab has fallen off and a fresh layer of skin has formed underneath,” the WHO said on Saturday.
The ECDC also urged infected patients to abstain from sexual activity and close physical contact until their rash heals. It said they should especially avoid close contact with immunosuppressed people as well as pets or wildlife.
“If human-to-animal transmission occurs, and the virus spreads in an animal population, there is a risk that the disease could become endemic in Europe,” the European health agency warned on Monday.
Close contacts of monkeypox cases should also self-monitor for the development of symptoms for 21 days after the last exposure.
Belgium has already introduced a compulsory three-week quarantine for monkeypox patients, while UK health authorities are advising “high-risk” contacts of infected patients to also self-isolate for 21 days.