Guinea worm disease is a painful and debilitating disease that used to be common in Asia, the Middle East, and many countries in Africa.
It’s now close to being eradicated worldwide. This success is thanks to an eradication program that has focused on water treatment and filtration, public education, and providing safe sources of drinking water to reduce its spread.
The disease is caused by a parasite called guinea worm ( Dracunculiasis medinensis ). The worm’s larvae are carried by water fleas found in stagnant water in ponds, open wells, and freshwater lakes.
When someone drinks contaminated water, the larvae can invade their stomach and intestines.
Over time, they mature into adult worms – with female worms growing up to around a meter in length – and crawl through people’s connective tissue, joints, and bones. This growth leads to arthritic conditions, which can debilitate people for months. Around one in two hundred infected people develop a permanent disability from the disease. 1
Around a year after the infection, the worm begins to emerge from the skin through a painful blister. This process also increases the risks of other infections.
People often try to find relief from the infection by putting their blisters in open water. This might bring some temporary relief for them, but makes it harder to eliminate the disease. In the water, the worm can release its own larvae and if the water contains water fleas, this restarts the life cycle of the guinea worm.
The disease can be treated with pain medication and antibiotics, and by carefully removing the worm when it emerges. 2
This parasite has troubled humans for a long time. There are records of guinea worm disease dating back thousands of years. 3
It was endemic in Asia, the Middle East, and many countries in Africa in the early twentieth century. 4
It was common in poor remote villages without access to clean drinking water . This was because sources of stagnant water – such as large open wells and ponds – could be contaminated by water fleas that contained guinea worm larvae.
Unfortunately, people do not develop immunity to the disease if they have been infected, which means it was common for people to be reinfected several times. For example, in the 1960s, in some villages in South India, more than 70% of adults infected once had been reinfected later on, and 10% had been infected at least 10 times. 5
By the 1980s, guinea worm disease was known to be endemic in 20 countries in South Asia and parts of Africa. We see this in the map, which shows the number of reported cases by country in 1989.
In 1986, around 35,000 cases were reported to the World Health Organization (WHO). As surveillance improved, the number of detected cases increased to 890,000 in 1989.
Unfortunately, there are no vaccines against guinea worm disease.
However, the disease has several features that make it easy to prevent.
First, humans are the main ‘host’ of the disease, with only a few exceptions. 6 The worm larvae are unable to survive for more than a few weeks in water fleas. 7 This means the worms can easily die out if they are prevented from infecting humans.
That brings us to our second point: we know how to stop it from infecting people. When people avoid drinking contaminated water that contains water fleas and guinea worm larvae, they are prevented from being infected.
Third, the disease is seasonal. People infected in one season tend to release worms a year later, which restarts the seasonal cycle. In the past, when villages halted the spread of worms in a single season, the disease stopped entirely unless it was reintroduced from somewhere else. 8
The world has made tremendous progress in reducing the burden of this disease with the knowledge of how to prevent it from spreading.
The campaign to eradicate guinea worm disease began in the 1980s. It was led by a number of organizations including the Centers for Disease Control and Prevention in the United States (US CDC), the Carter Center, the WHO, and the United Nations Children’s Fund (UNICEF). 9
Village volunteers have played a major role in the eradication program. They provide people with water filters and larvicides, educate them about where to drink clean water, record cases, help treat patients who are suffering from the disease, and prevent them from releasing worms into the water. 10
Another key driver of progress is access to improved drinking water sources, which has become more common in many countries.
You can see the change since the start of the eradication campaign in the chart. Cases of guinea worm disease declined rapidly across many countries.
Over 890,000 cases were recorded worldwide in 1989. By 2021, there were just 15.
Almost all of the 15 cases were recorded in Chad.
In many countries, guinea worm disease has been completely eliminated.
Countries are certified as free of guinea worm disease if they have reported zero indigenous cases for at least three consecutive years while having active surveillance. 11
On the map, you can see which countries are certified as being free of guinea worm disease. They are shown in blue. Using the timeline at the bottom of the chart you can see how each country’s status changed over time.
In 1996, 16 countries were known to be endemic for guinea worm disease. By 2021, only five countries remained endemic – Mali, Chad, South Sudan, Ethiopia, and Angola.
To eradicate guinea worm disease globally, there are several challenges we need to overcome.
We don’t know, for example, whether the Democratic Republic of Congo is free of guinea worm disease, because levels of monitoring have been insufficient to confirm it. This is shown in the map above.
A general challenge is that it takes around a year after infection for the worm to emerge from a person’s body. This is why countries need to monitor for new cases for several years after they have reported zero cases, in order to achieve certification.
Another problem is that a few countries, such as Chad and Ethiopia, have recently had outbreaks linked to dogs infected with the worms, which had not been seen before. That means extra efforts have been needed in recent years to prevent infections in dogs in those regions. 12
Finally, it has been difficult to eliminate guinea worm disease in countries with violence and conflict, where healthcare workers are less able to treat and prevent infections. 13
Despite these challenges, there has been a massive decline in guinea worm cases over time. Only 15 cases were reported globally in 2021. The world is so close to the goal and with dedicated effort, we may soon achieve it. After thousands of years, the entire world may soon be free of this debilitating disease.
Keep reading on Our World in Data:
Acknowledgments: Hannah Ritchie and Max Roser provided very helpful guidance and comments that helped improve this post.