Mpox: what we know so far

It's important to remember that mpox is highly unlikely to become a global pandemic like Covid-19.

That doesn’t mean authorities shouldn’t act quickly. Although the current strain appears to be mild, mpox can cause severe disease and, rarely, even death.

At this stage of the current mpox outbreak, contact tracing can break the chains of transmission and, if done well, should be highly effective at preventing the situation from escalating.

We should be concerned. The number of cases and their locations indicate a degree of community transmission in multiple countries, many of which have never recorded mpox cases.  

On Saturday 23 July 2022, the World Health Organization (WHO) declared the mpox outbreak a Public Health Emergency of International Concern. 

WHO director-general Dr Tedros Adhanom Ghebreyesus said that the rapid worldwide spread of mpox through new routes of transmission that aren't well understood was a key factor in the decision.

Mpox is endemic to several regions in Africa, but it has appeared in other countries before. Usually this has been isolated cases or outbreaks closely connected to travel to Africa or the international pet trade, as was the case in an outbreak in the US in 2003.  

What’s different about this outbreak is that, at the time of writing (23 July 2022), more than 16,000 cases have been reported in 75 countries and territories, along with five deaths. This includes growing case numbers in Europe, the Americas the Middle East and Australia, far from the countries of Central and West Africa where mpox is endemic.

Unusually, most cases so far have been concentrated in a specific community – those who identify as gay, bisexual, or other men who have sex with men (MSM). We don’t fully understand the reasons for this, and further research is needed to understand why this community is particularly affected.

It's important that engagement with the community is conducted in a productive manner and stigmatising actions or narratives avoided. Stigmatising mpox or any other infection runs counter to the goals of public health, making prevention of escalation much harder.

Unlike the coronavirus that causes Covid-19, mpox is not thought to be infectious during a person’s incubation period, meaning people are not thought to spread the disease if they don't have symptoms. It also requires close contact to spread. Combined, these factors are likely to limit how widely the disease is transmitted.   

However, it can infect different animal species. There is a worry that mpox could become endemic in new parts of the world, particularly in areas with poor disease surveillance, if it manages to become established in animal populations. 

So, while it’s unlikely that mpox will become the next pandemic, if it were to enter new animal populations there is a small but real risk that we could see further outbreaks outside of its historically endemic range.

The WHO had previously ruled out declaring mpox a global emergency on Saturday 25 June 2022.

Now, scientists need to better understand the origins of this outbreak and whether the virus itself has changed. This information should come to light as more genomic sequences become available.

We already have key tools to control the disease – effective vaccines and treatments. These were primarily developed to control smallpox, not mpox, so research to understand how well these work against mpox is a priority in the current outbreak.

Although data is limited, it’s thought the smallpox vaccine provides 85% protection against mpox. The NHS (National Health Service) in the UK is already using it for close contacts of those who have tested positive. Many governments have historically maintained stockpiles of smallpox vaccine for emergency use, which are now being accessed to combat the spread of mpox. The USA, EU, UK and others have also requested additional purchases of vaccines.   

Vaccines prevent infection, but we also need drugs or treatments for people who are sick with mpox. Because the disease is so rare, it’s difficult to test drugs in the real world. However, a drug called tecovirimat or 'TPOXX' has been shown to be safe and effective in animal studies at treating disease. This is now being used on a limited level in those who get sick, which allows us to further understand how effective it is for treating people.

The expanded use of TPOXX and the smallpox vaccine in preventing and treating mpox is an important opportunity to collect data on the effectiveness of these tools. Improved knowledge on these may stop the disease spreading and could also help the African countries where the disease is endemic to better prepare for future outbreaks.

Now is the time for careful surveillance and rapid research. A robust disease surveillance system is what first detected community spread of mpox in the UK, and researchers and governments rapidly began to communicate and share data to better understand the spread between countries.

Public health authorities must work with local communities to continue monitoring the spread of the virus, break chains of transmission and ensure that any changes to transmission or severity are identified.  

Dr Josie Golding, Head of Epidemics and Epidemiology at Wellcome, said the WHO's decision to declare mpox a global health emergency should serve as a stark reminder to world leaders of how vulnerable we are to new infectious disease outbreaks.

"Governments must take this more seriously and work together internationally to bring this outbreak under control," added Golding. 

“Without this swift and concentrated action, mpox will continue to infect even more people unnecessarily and become established in more populations, including the risk of reverse spillover into animals."   

As the last two years have made clear, building robust systems of cooperation are vital if we are to prevent infectious diseases from escalating. Information from contact tracing, genomic studies and vaccine and therapeutic use must be shared across nations and public health bodies to inform development and use of future interventions and understand how this outbreak began.

The virus name has been changed from "monkeypox" to "mpox" throughout this article in line with recommendations from the World Health Organisation (WHO).

This article was first published on 1 June 2022.