Contact Tracing

Finding and Tracing Ebola

Tracing contacts and monitoring their health ensures that sick people can be identified immediately. They then can be isolated and treated, so that each chain of transmission can be stopped. 

This infographic was created during the Ebola epidemic to explain contact tracing and its importance to controlling and preventing the disease. People identified through contact tracing were monitored for 21 days after their last contacts with people with Ebola—21 days is the amount of time for symptoms of a new Ebola infection to appear. 

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What Is Contact Tracing? Ebola Response Infographic. Produced by CDC's Division of Creative Services

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Kari Yacisin, CDC responder, heading to a remote village in Guinea to complete a day of contact tracing with her team. 

On paper, case-finding and contact tracing—the identification and locating of individuals with direct contact to persons with the disease—are very methodical disciplines. In reality, they are complicated tasks requiring a multidisciplinary approach, particularly in the case of the Ebola epidemic. Epidemiologists, clinicians, geographers, laboratorians, behavioral scientists, social mobilizers, logistics managers, community leaders, and anthropologists are among those who participated. 

Numerous challenges to case-finding and contact tracing persisted throughout the epidemic: the spread of the disease in both rural and urban areas, distrust of government and outsiders, delays in seeking treatment and inadequate treatment centers, cultural beliefs, fear and stigma. 

Kuhar, David

Dr. David Kuhar

Dr. David T. Kuhar, medical officer in CDC's Division of Healthcare Quality Promotion, describes his experience explaining contact tracing to others.

Narra, Rupa

Dr. Rupa Narra

Dr. Rupa Narra of CDC's Waterborne Disease Prevention Branch served as an officer in the Epidemic Intelligence Service. In her oral history, she remembers her experience with contact tracing in Guinea. 

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CDC responders using OpenStreetMap data on a tablet to help navigate to this small village between Kambia town and Kabaia in Kambia District, Sierra Leone

Maps: Essential Tools for Contact Tracing

Teams responding to the Ebola outbreak in West Africa often faced the challenge of finding people and communities living in remote areas. Maps of these regions often didn’t exist, or were incorrect or outdated. Basic information—locations of houses, buildings, villages, and roads—was not easily accessible.

To help the response effort, volunteers from around the world used an open-source online mapping platform, called OpenStreetMap (OSM), to create detailed maps of Guinea, Sierra Leone, Liberia, and parts of Mali. The Humanitarian OpenStreetMap Team (HOT), a U.S.-based, non-profit organization that uses OSM data and tools to prepare and respond to humanitarian disasters, took the lead.

Because OSM data can be downloaded for free, volunteer mappers generated data useful to CDC and other agencies involved in the Ebola response. Over the course of the epidemic, more than 2,500 volunteers mapped more than 750,000 buildings and hundreds of kilometers of roads, resulting in detailed maps of affected West African communities. Not only did these maps help first responders and other organizations around the world, they also contributed to the national information infrastructure essential to the recovery and rebuilding of affected regions.

Magazine Wharf Cluster Tracking, Sierra Leone, June – August, 2015

Epidemiologists used a whiteboard at the Western District Ebola Response Center (DERC) to track the Ebola virus from the Magazine Wharf cluster, June–August, 2015. Magazine Wharf is located on the waterfront in a densely populated, commercial area of Freetown with limited electricity and toilet facilities. For these reasons, the disease had the potential to spread rapidly. The board recorded the initials, sex, age, date of onset, and relationships (including transmission by generations) between confirmed Ebola patients. It was continually updated as new information was received.

The Magazine Wharf cluster, the last Ebola cluster in Sierra Leone occurred due to community transmission, was a microcosm of the Ebola control effort: it required investigation and control of Ebola transmission during funeral rites, at healthcare facilities, and in the community among friends, coworkers, and family members.

This image is an example of how data, as seen on a whiteboard, are then "cleaned up" into an epidemiological diagram.

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Western-Magazine Wharf Cluster diagram, July 7, 2015. Produced by CDC's Incident Management Team