What to know about contact tracing

Early in the COVID pandemic, the United States tried contact tracing to help reduce the spread of illness, re-open local economies, and get people back to work.

What’s involved in this decades-old disease-control strategy, and how does it help efforts to keep people safe from infection?

The basics of contact tracing

Contact tracing is an important tool for slowing the spread of disease. It’s the practice of tracking people who have been exposed to an illness, notifying them, and teaching them what to do next. This can help them get treatment quickly and prevent them from passing the disease to others. Contact tracing is also used by scientists to gather data about how an infection spreads, so they can make informed decisions to protect public health.

The success of contact tracing depends heavily on the disease being monitored. It also depends on several social, cultural, and political factors. These can include:

• The way a disease is transmitted
• How long a disease remains infectious
• How long someone might be asymptomatic before showing signs of the disease
• How quickly and effectively lab tests can identify the disease in samples
• What kind of treatments exist
• The abilities of contact tracers to collect names of contacts
• The cooperation and participation of everyone in a community

During outbreaks of a disease, government public health agencies may hire people to work as contact tracers. These workers must understand and be sensitive to the culture of the communities they serve and build trust with others during lengthy and potentially sensitive interviews. They also offer basic counseling and help refer people to resources within their communities.

Contact tracing and COVID

Contact tracing has long helped to control outbreaks of highly contagious diseases. It played an important role in controlling smallpox, for example, which was declared eradicated by the World Health Organization in 1980. Health officials have also used this strategy to respond to sexually transmitted infections like HIV, syphilis, and gonorrhea, as well as other contagious diseases like measles and chicken pox. Contact tracing helped control SARS in 2003 and the 2014 Ebola virus outbreak, as well.

Given its history of success, U.S. scientists employed contract tracing once again during the COVID pandemic. By December 2020, about 70,000 people worked as contact tracers. But the quick spread and sheer size of the outbreak challenged efforts to coordinate.

“It’s something that health departments do all the time,” says Christopher Ohl, MD, professor of infectious diseases at Wake Forest University in Winston-Salem, North Carolina. “They just [hadn’t] had to do it on this scale before.”

Lack of rapid, reliable, and accessible testing presented obstacles for contact tracers, as did communication issues, such as language barriers. Some people didn’t want to be quarantined for having COVID, while others resented what they saw as government surveillance and overreach. Once the COVID vaccine rollout began in late 2020, contact tracing started to fall by the wayside.

Research suggests, however, that contact tracing ultimately helped to contain the virus worldwide. A 2023 systematic review published in Global Epidemiology found it was particularly useful in areas where quarantines were effectively employed.

The future of contact tracing

The painstaking process of contact tracing plays a vital role tracking and containing outbreaks and preventing resurgences of disease. But it’s important to remember: Contact tracing only works when the public participates. It’s up to us to help keep ourselves and our communities healthy and safe.