Monkeypox: How is biodiversity loss linked to emerging zoonotic diseases?

A series of monkeypox outbreaks around the world have raised concerns over the potential for more diseases to cross into humans.

While monkeypox outbreaks are not uncommon in its native African range, alarm has been raised after the disease has begun spreading in countries outside this region.

At the time of writing, hundreds of cases have been confirmed in the UK, with infections also recorded in Australia, the USA, Canada and European nations.

Cases in the UK are currently being monitored by the UK Health and Security Agency (UKHSA) and the World Health Organisation (WHO), but it is not thought likely it will spread widely.

Dr Colin Brown, Director of Clinical and Emerging Infections, UKHSA, says, 'It is important to emphasise that monkeypox does not spread easily between people and the overall risk to the general public is very low.'

'We are working with NHS England and NHS Improvement to contact the individuals who have had close contact with the case prior to confirmation of their infection, to assess them as necessary and provide advice.'

'UKHSA and the NHS have well established and robust infection control procedures for dealing with cases of imported infectious disease and these will be strictly followed.'

Following the swine flu pandemic of 2009, the ongoing COVID-19 pandemic, and now monkeypox, the interaction between humans and the environment is helping to drive the emergence and spread of both known and unknown diseases. 

What is monkeypox?

Monkeypox is a DNA virus which is a member of the Poxviridae family. It is part of the Orthopoxvirus genus alongside diseases such as cowpox and smallpox. There are two clades of the virus, one from West Africa and one from the Congo Basin.

The Congo Basin was the location where the virus was first discovered in humans in 1970, though its presence in animals was first detected 12 years earlier. While it was first identified in a monkey, giving the disease its common name, it is generally thought to be spread by rodents such as mice, rats and squirrels.

Since its discovery, there have been periodic outbreaks of the disease within western and central Africa, but cases have generally been rare outside this region. 

One of the most significant outbreaks outside Africa came in 2003, when over 70 cases of monkeypox occurred in the USA. The infections were linked to the import of animals such as Gambian giant pouched rats and rope squirrels for the exotic pet trade which were carrying the virus.

The first case in the UK was in 2018, following an individual travelling from Nigeria to Plymouth. Three more cases were reported over the next year, but the virus did not spread widely.

The current international outbreak began in May 2022, when a case was confirmed in the UK. However, a recent study of this strain of monkeypox suggests that there was no single introduction event and could not rule out that the virus had been circulating before it was first detected.

Since then, the disease has spread across the world. Thousands of cases have been reported, with the vast majority in Europe. During this outbreak, there has been one death attributed to monkeypox in Nigeria.

An initial study of the current strain of the virus, published in Nature Medicine, found it originates from the West African monkeypox clade. It differs from the 2018-2019 strain by around 50 changes in its genome. This is as much as 12 times more than would normally be expected, suggesting the virus is undergoing accelerated evolution.

In the UK, efforts to combat the spread of monkeypox include the use of the smallpox virus Imvanex, which is to be offered to those at a higher risk of being exposed to the disease. 

How does monkeypox spread, and what are its symptoms?

The disease is spread through bites from infected animals, as well as through coming into contact with respiratory droplets found in coughs and sneezes, lesions, and the bodily fluids of infected individuals.

After exposure, it can take anywhere between five days to three weeks for symptoms to become apparent. These symptoms include a high temperature, headache, muscle aches and swollen glands. 

Between a day and five days later, the rash which gives the disease its name develops. It generally develops on the face before spreading to the other areas of the body. The rash develops into small blisters, which eventually scab over and fall off.

The disease normally clears up in around two to four weeks. Congo Basin monkeypox generally causes more severe disease than the West African clade, but both are considered self-limiting as they normally clear without additional treatment.

However, anyone who suspects they may have symptoms of the disease is asked to contact their GP or the NHS.

Dr Sophia Makki, Incident Director at UKHSA, says, 'We continue to see a steady increase in monkeypox cases. We're reminding everyone to be aware of the symptoms of monkeypox, particularly if you’ve recently had new or multiple sexual partners, to help prevent further spread and protect others.'

'If you have a rash with blisters, or any other monkeypox symptoms, don’t go to events, meet with friends or have sexual contact. Instead, stay at home and contact 111 or your local sexual health service for advice. Please contact the clinic ahead of your visit and avoid close contact with others until you’ve been reviewed by a clinician.' 

How is monkeypox linked to biodiversity loss?

Most of the world's species remain undiscovered. While 1.2 million species have been scientifically described, it is estimated that there are around 8.7 million species of animals, plants, fungi and their relatives on Earth.

While some of these species might be right under our noses, others are probably residing in unexplored and inaccessible areas of the world. As we increasingly encroach into natural habitats such as rainforests, there are more chances that we will come into contact with new species. 

These species may harbour viruses and bacteria with the potential to cause disease that humans have never encountered before. While these diseases may have been circulating naturally in the environment for many years, human intervention can cause them to jump into other species – including ourselves.

For example, COVID-19 and Ebola virus are both diseases which come from a reservoir of wild animals. In both cases, humans moving into forests or consuming wild animals are thought to have been responsible for the disease crossing the species barrier.

Similarly, monkeypox is believed to have originated in the rainforests of western and central Africa, where over 500 square kilometres (roughly the same size as the Isle of Man) is being lost each year. 

Deforestation is also contributing to climate change, which also has impacts on zoonotic diseases. Rising temperatures cause animals to change where they live as they adjust, making them more likely to enter areas of human habitation.

A recent study estimated that over 15,000 diseases will spread into a new species for the first time in the next 50 years as a result of rising global temperatures. 

How prevalent are zoonotic diseases likely to become?

The simple answer is that we don't know. It is likely that many diseases which are already of concern, such as influenza, SARS and Ebola, will continue to pose a threat throughout the 21st century, re-emerging periodically when conditions and circumstances are suitable for them to spread.

There are also many diseases which currently infect animals that could gain the ability to infect humans or other species and become zoonotic. This could either occur naturally through natural selection or as the result of artificial intervention.

Finally, there are many diseases that we are not yet aware of. As agriculture expands, and human populations grow, there is an increasing chance of encountering an unknown zoonotic disease. 

The international trade in plants and animals could also bring these diseases to new areas of the world, far beyond their natural range.  

What can be done about zoonotic diseases?

Combatting zoonotic diseases is not a simple process, and requires a variety of different steps to prevent and mitigate possible impacts.

The easiest step is to reduce the chance for human and animal populations to come into contact. This can be achieved by reducing land use change and biodiversity loss as much as possible, such as by creating more protected areas. 

Reducing our demand for materials extracted by mining or deforestation will also lessen the chance of disturbing hosts of new zoonotic diseases. Changing our diet to more sustainable and plant-based alternatives reduces the need for agricultural land, which is one of the leading causes of land use change.

As well as prevention, we also have to look at cure. Research needs to continue into creating new vaccines, as well as antiviral and antibiotic agents that can help us treat diseases when they arise.

This can be assisted by the monitoring of human and wild animal populations to look out for signs of a new zoonotic disease spreading. This will allow public health organisations to step in and prevent an outbreak from becoming a pandemic.

Looking into the past can also be helpful. Studying specimens held in museums and natural history collections around the world can give scientists an idea of how diseases and animal populations are changing over time which can help anticipate what may happen next.

Collectively, these steps can help humanity prepare itself for the diseases the Anthropocene has in store.