Health workers have an unusual tool for fighting disease that turns our old thinking about treatment on its head. I saw it at work recently in a remote hilltop village in Tanzania, where I joined a group of health workers going from house to house to distribute medicine to wipe out lymphatic filariasis, one of the world’s most painful and debilitating diseases. 

At each home, one health worker told the family about the swollen limbs, disfigurements, and other symptoms of the parasitic disease. Another carried a tall stick to measure the height of each family member to determine the correct dosage. Then, if they were willing to be treated, the parents and children took their pills and washed them down with a cup of water before our team moved on to the next house.

What was surprising about this effort is that none of the people who took the medicine were sick.

The village I visited was participating in what’s known as a mass drug administration campaign, which seeks to treat everyone against a disease—even if they are not actually infected or show any symptoms. Typically, of course, the sick are the ones who get treated, not the people who are healthy. But when it comes to combating some diseases, like lymphatic filariasis, it’s critical for health workers to try to treat the entire at-risk population to break the cycle of transmission. If not, the disease could continue to be spread by those who are not aware they are infected.

Ten countries have successfully eliminated lymphatic filariasis in this way, including Togo, which this year became the first country in sub-Saharan Africa to wipe out the disease. Still, more than 800 million people in 52 countries worldwide remain threatened by lymphatic filariasis.

Mass drug administration is not only effective against lymphatic filariasis, but also other neglected tropical diseases, including schistosomiasis, onchocerciasis, trachoma, and soil-transmitted helminths. These diseases go by names that are largely unknown and often difficult to pronounce. But it should be easy to understand why we should all care about them. They afflict people living in the poorest countries and cause untold suffering.

Lymphatic filariasis is one of the worst of these diseases. It’s caused by a parasite that’s spread by mosquitoes, and in the severest cases people may develop swollen limbs, a thickening of the skin known as elephantiasis, or other severe disfigurements. Beyond the pain and disabilities they experience, people affected by the disease are often ostracized by their communities and are unable to work, sinking them deeper into poverty.

To combat lymphatic filariasis, health officials could test everyone and then treat only those people who are infected. But testing the population for these diseases would be expensive and slow. The medicines used for treatment (ivermectin and albendazole), however, are inexpensive and have no side effects, making mass treatment a more effective approach to protect people from the disease. (And thanks to the generosity of the many pharmaceutical companies, billions of doses of these and other medicines combating neglected tropical diseases are being donated for free.)

Like many countries running mass drug administration programs, Tanzania’s biggest challenge is treating enough of its population at risk of the disease. To break the cycle of transmission, health workers must treat at least 65 percent of the population every year for 5 to 10 years. As you might imagine, meeting this target year after year is not easy.

Health officials must have strong public awareness campaigns, thousands of trained health workers, a well-organized supply chain to distribute medicines to the remotest corners of the country, and regular disease surveying to track their progress. At the same time, the program provides treatment and care for people who are suffering from the debilitating symptoms of the diseases.

Walking from door to door in the village with the health workers, I was struck that perhaps the most important element of the program is trust. Taking the medicine is strictly voluntary, making it important that the health workers distributing it earn the confidence of the community.  The health workers I met certainly had. They were knowledgeable, passionate about their work, and clearly cared about the community they were serving. At each home, they took the time to explain the goal of the program and address any of the villagers’ questions or concerns. Thanks to their hard work the latest survey of lymphatic filariasis in their district showed that the cycle of transmission had been broken. For the first time, the village was not at risk of the disease.  

By 2020, Tanzania hopes to eliminate lymphatic filariasis entirely within its borders. Based on what I saw in this village, I’m optimistic they will.