Is Contact Tracing Getting Enough Attention in U.S. Coronavirus Response?
There is a consensus forming among public health experts about the kinds of capabilities that the U.S. needs to build up and apply in order for communities to successfully combat COVID-19 and transition from our current social distancing/sheltering-in-place moment to something resembling normal daily life. Think tank reports, many articles, and numerous op-eds from experts have all converged around putting certain key elements in place, such as:
- Greatly scaling up diagnostic testing capacity to identify cases;
- Growing the number of available hospital and intensive care beds;
- Increasing the availability and improving the distribution of necessary supplies, including personal protective equipment and ventilators; and
- Scaling up contact tracing and quarantining of close contacts of known COVID-19 cases.
The first three points on the list above are immediate needs and have been front and center in debates around COVID-19 response, from the White House daily press conferences to governors’ and Mayors’ discussions of the needs in their states and cities. However, the fourth point – contact tracing – has been emphasized much less. In three recent White House Coronavirus Task Force Press conferences, for example, the needs around testing, hospitals, and supplies such as masks and ventilators were mentioned dozens of times, while contact tracing was mentioned just once, in passing.
Contact tracing is the process of identifying, assessing, and managing people who have been exposed to a contagious disease to prevent onward transmission. It is a key component of infectious disease control and response. And, despite being mostly ignored in politicians’ press conferences to date, contact tracing is going to be a crucial piece of the puzzle for eventually suppressing and containing the virus, allowing people to congregate in public, and letting people go back to work again. Once social distancing measures have had the effect of turning the tide on local epidemics, contact tracing can then be used to identify and interrupt ongoing transmission chains and allow public health authorities to understand the extent of spread in a community. Effective contact tracing has been an essential component for successful coronavirus responses in other countries, including in China, South Korea, Singapore, and Germany.
However, the challenges facing a contact tracing effort here are daunting. For one, local public health departments, currently responsible for contact tracing efforts, are already stretched thin and in many cases overwhelmed by response needs, having been weakened by budget cuts for years. Undertaking contact tracing, even when coronavirus case numbers are falling, will still be a monumental effort. For example, if at least 750,000 tests per week are needed to have a decent chance of identifying most COVID-19 cases in the U.S. (as recommended recently by an expert group), and assume 10% of those tests are positive (a target benchmark cited by experts), that would mean 75,000 cases whose contacts would have to be investigated each week. This is similar to the scale of efforts in Wuhan, China in February, when 1,800 contact tracing teams of five people each traced tens of thousands of contacts each day. Hard to imagine there would be enough workers trained and equipped to do contact tracing in the U.S. in a few weeks’ time without a truly massive, nationally-coordinated scale-up effort.
To complicate things further, we know some proportion of asymptomatic and pre-symptomatic transmission occurs, making it that much harder to identify all cases to isolate, even with sufficient testing capacity. Newly published modeling suggests that, given the challenging characteristics of Covid-19 like asymptomatic transmission, the standard approach to contact tracing – with people calling and investigating all close contacts of identified cases – will likely face limitations in effectively interrupting enough community chains of transmission. What’s likely needed to supplement traditional contact tracing are more automated, technological approaches using mobile phones and apps. For example, notifications could be automatically pushed to other phones which were determined to have been in proximity to a known case, or an app could be created and pushed to people in affected geographic areas, which would automatically alert them if they may have been in contact with a case. This approach is faster, and likely more effective. It has already been used in places that have been successful in interrupting the spread of disease such as China, South Korea, and Singapore.
Recognizing this, some private and academic groups have begun to create just these kinds of resources and push for digital participatory, crowd-sourced contact tracing, such as: NextTrace, Covid Watch, Trace Together, and Safe Paths. These initiatives are only starting to coordinate and get visibility. At the same time, concerns about privacy have already been raised and would need to be addressed if such a route were pursued.
Reasonably, only the federal government could truly bring order and achieve a national, coordinated effort on the scale (and expense) necessary to address the problem. It would require ensuring that most Americans are connected to the efforts through their phones and sufficient attention is given to privacy concerns that will undoubtedly arise. To date, however, and despite the fact that the CDC Director has indicated he expects to pursue aggressive early case definition, isolation, contact tracing in states that, thus far, have limited transmission, there is little evidence of a genuine federal effort to build up capacities to do this, or to bring together the valiant but scattershot efforts from the private sector. Even if a more widespread testing effort is, eventually, implemented, it is hard to see how the contact tracing gap will be easily closed.