Commentary: Epidemiologists and contact tracers are disease detectives

By Dr. Jennifer Horney and Colten Strickland

Among all the responsibilities expected of epidemiologists, if any validate the designation as “disease detective,” it is contact tracing.

Contact tracing has been a crucial part of public health for decades. In conjunction with mass vaccination and surveillance, contact tracing plays a key role in our ability to combat communicable diseases in our society. This has successfully led to major public health accomplishments in the United States in the past 100 years, such as the eradication of smallpox and the elimination of polio, measles and rubella. And it is a major part of our strategy to fight the COVID-19 pandemic.

Contact tracing is used by public health staff to identify the contacts of a person who has been infected with a communicable disease. Each state maintains a list of what are known as reportable conditions. Health care providers and laboratories are required to report cases of these conditions to the Division of Public Health, who in turn report to the Centers for Disease Control and Prevention. This, in part, is how outbreaks are detected.

Dr. Jennifer Horney

Reportable conditions include vaccine-preventable diseases like measles and chickenpox; sexually transmitted diseases like gonorrhea and syphilis; food- and waterborne diseases like salmonellosis and listeriosis; vectorborne diseases like West Nile virus and Zika; and diseases that could be used as part of an intentional or bioterrorism attack, like anthrax plague or smallpox. COVID-19 was made a reportable condition nationally April 5.

When cases of these and other diseases are reported to public health authorities, they frequently begin an investigation that includes contact tracing. Contact tracing involves an epidemiologist or other public health staff person working with patients to recall everyone they may have had contact with during the time that they may have been infectious. A contact tracer, sometimes called a disease investigation specialist, will then reach out to all those contacts to assess whether they should be tested, seek medical care or perhaps simply monitor themselves at home.

The advice provided by a contact tracer for COVID-19 will be different than for many conditions. This is because, at the present time, there is no treatment for an individual infected with COVID-19. So, the contact tracer will provide information to the contacts of a person infected with COVID-19. This might include information on how to effectively self-quarantine at home or what symptoms to be looking for. In this way, through contact tracing, the transmission of a disease – even one without a vaccine or pharmaceutical treatment – can be interrupted and the spread of the infection can be reduced.

The work of contact tracers is complicated by the fact that most conditions have variable incubation periods and periods of infectivity and that many infections can be asymptomatic. Other complications include respondents’ difficulty in remembering all the people they may have encountered – in public health, we call this recall – and concerns about privacy and confidentiality.

Although public health agencies are endowed with extensive legal authorities, particularly during a public health emergency, successful intervention to ensure that outbreaks of communicable diseases are adequately addressed relies on the cooperation of the public. All people impacted by COVID-19, or any other reportable conditions, have the right to privacy – that is, to keep their health information private. Public health staff are trained to ensure confidentiality to keep any health data that they are entrusted with private.

Colten Strickland

In short, it is important for us to acknowledge the role of contact tracing for “quenching” the COVID-19 pandemic and helping keep us on a path toward safely relaxing Delaware’s stay-at-home guidelines. Public health officials have a track record of success in protecting citizens, but to do this, it sometimes requires the cooperation of us all. With no vaccine in sight, contract tracing is a crucial part of reopening our economy and society.

Jennifer Horney, Ph.D., MPH, is a professor and founding director of the epidemiology program at the University of Delaware.

Colten Strickland, MPH, is a doctoral student in the epidemiology program at the University of Delaware.