As the world grapples with the monkeypox outbreak, countries with flare-ups of the viral disease have been offering vaccination to contacts of infected people and those in groups considered as being at risk.
At the weekend, the World Health Organisation declared the outbreak a public health emergency of international concern, the first since Covid-19.
For most people, symptoms such as rashes on the face, palms and other parts of the body, and a fever, are not serious, although individuals with a weakened immune system, pregnant women and children may be more at risk and the disease can prove fatal.
With cases having exceeded 18,000 across 75 countries this year, concerns have been raised about whether will it be possible to control the spread of a disease that, until recently, was largely confined to west and central Africa, with occasional, typically short-lived appearances elsewhere.
Figures compiled by the US Centres for Disease Control and Prevention show that America has recorded more than 3,800 cases this year, with Spain at more than 3,000 and the UK and Germany reporting more than 2,000 infections.
What difference does declaring a public health emergency make?
The WHO’s decision to name the outbreak a public health emergency is “a warning signal” about the seriousness of the outbreak, said Dr Bharat Pankhania, a senior clinical lecturer at the University of Exeter in the UK.
“It’s an alert, it’s raising a red flag,” he said. “It’s telling everyone we should be doing something about it and all nations with all their expertise should go into action stations.”
Prof Paul Hunter, an infectious diseases specialist and professor in medicine at the University of East Anglia in the UK, said he thought the world could “get on top of” the outbreak.
A reason for this is that the disease is “not that infectious”, with the R number being less than 1.0 among the general population, meaning that one infected person on average passes the infection on to fewer than one other person.
But Prof Hunter said that among men who have sex with men and have multiple partners, the R rate is between 1.4 and 1.8, so many recent cases have been among this group.
Indeed the global outbreak has been driven by patterns of behaviour often linked to dating apps, suggested Prof Ian Jones, professor of virology at the University of Reading in the UK.
“It’s very much a social phenomenon,” he said, adding that there was no indication that the outbreak was due to the virus spreading faster because it had changed.
Drawing a parallel with what happened with HIV, the virus that causes Aids, Dr Pankhania said that monkeypox could go on to spread more widely in the general population if the current outbreak was not dealt with.
How can the outbreak be controlled?
Health authorities should use contact tracing and vaccination of at-risk groups, including medical staff who may come into contact with cases, according to Dr Pankhania.
One vaccine used against monkeypox is an updated version of an old smallpox vaccine, but this contains a virus that, although weakened, can sometimes cause disease in people with a compromised immune system.
A newer vaccine, called MVA but also known by various brand names, was also originally developed against smallpox.
It is being used by some countries such as the UK and is considered safer because the virus it contains has been more heavily weakened and so is unlikely to cause illness, although there are reported supply constraints.
“You can get at least 70 to 75 per cent protection, which is better than nothing and pretty good to be honest,” Dr Pankhania said.
Unlike with Covid-19, vaccination programmes need only to concentrate on at-risk groups, rather than the general population, where rates of spread are extremely low.
“There just isn’t a case for mass vaccination,” said Prof Jones, saying that the modest number of cases globally meant a universal campaign was not appropriate.
While there have been concerns expressed that some countries have not done enough to ensure that at-risk groups are vaccinated, Prof Hunter said there was evidence that spread may have peaked.
Even if the current outbreak is stamped out, monkeypox is likely to continue to emerge periodically across the world because in West and Central Africa — but not outside these regions — rodents are a “reservoir” for the disease and can spread the virus to people who are bitten or who eat uncooked meat.
“There’s always a risk they could have an outbreak that spills into the high-risk group again,” Prof Hunter said.
Vaccination campaigns under way
The UK's National Health Service is stepping up its monkeypox vaccination programme.
Health officials said 100,000 more doses of an effective immunisation had been bought.
The EU signed an agreement in June for the supply of about 110,000 doses of the Imvanex shot, known as Jynneos in the US.
Imvanex is currently authorised in the EU for the prevention of Smallpox in adults and has been recommended for use against monkeypox by the European Medicines Agency.
The US has delivered 300,000 vaccine doses and is working on the delivery of close to 800,000 more.