COVID-19 contact tracing
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April 16, 2020
What are common methods of contact tracing?
“Contact tracing is typically conducted by a trained disease investigator or, in smaller jurisdictions, a public health nurse who may have diverse responsibilities. Cases may be interviewed in person or over the phone to obtain basic demographic and identifying information for each person that has met criteria for exposure to the suspected case. In the event the case is a minor or is incapacitated, a relative or other informant may provide this information. In addition to contact information, investigators ask about the context and degree of exposure and any risk factors. In some cases, the source of an infection may be sought, or a site visit may be required to a place of common exposure. Partner notification is a related approach used in the control of HIV and sexually transmitted infections due to the sensitivity of contacts. In this example public health agencies assist cases in contacting their own partners to notify them of exposure.” (Posted April 16, 2020)
“Currently, contact tracing is a manual, very labor-intensive process involving public health staff, such as epidemiologists, calling individuals to obtain information. Per the World Health Organization, contact tracing involves detecting cases to identify their contacts; obtaining information and providing information to these contacts about the disease and their next steps due to their exposure; and, lastly, following up with contacts to determine if they develop signs and symptoms.
”Typically, upon identifying a case of COVID-19, information is obtained regarding who this case patient was exposed to or where the person was likely exposed to the virus during their incubation period. The incubation period is the time from being exposed to the infectious agent until the development of signs and symptoms. For COVID-19, information is obtained for up to two weeks prior to the case patient’s onset of symptoms. It’s important during contact tracing to make it clear to the case patient how exposure is defined and why you are asking certain questions. For example, with COVID-19 it is important to explain that a high level of exposure would be caring for a person who is suspected or has been confirmed to have COVID-19, while a low level exposure may be going to a grocery store for about a half hour or more without any close contact with people (< 6 feet), just causal contact while trying to maintain social distancing.
”In addition to understanding how the case patient became exposed, it’s also important to decide who the case patient may have exposed as well—their contacts. For COVID-19, per CDC guidelines, exposure is defined as possibly occurring up to two days before the case patient had any signs or symptoms and throughout the time period they had signs and symptoms or tested positive for the virus (the infectious period). The case patient should be informed clearly when they are infectious to prevent additional exposures. Lastly, in contact tracing you want to provide as much information as possible about the disease and virus to the case patient and answer all of their questions. It is imperative to make sure the case patient understands what both their and the epidemiologist’s next steps are with the information they provided. The case patient may be very scared and apprehensive about providing information, so it is so very important to reassure the person that the main goal is to protect them and the community you are both members of; provide a way for the person to contact you or someone else in public health if there are any additional questions or any additional information they can provide to help stop the spread of the virus. The entire process is then repeated with the contacts of the case patient.” (Posted April 16, 2020)
“Contact tracing is an old public health approach used particularly for TB and selected STDs, to identify individuals who may have been exposed and who may be incubating the infection and require treatment. As practiced in the past, it is labor intensive and requires substantial training of the those acting as contact tracers.” (Posted April 16, 2020)
What are the benefits of contact tracing in preventing further spread of COVID-19?
“Contact tracing is useful for a few purposes: treating people that may have been exposed, preventing new chains of transmission, identifying the degree of risk to people exposed to the case. For jurisdictions in the U.S. that have relatively few cases (now or in the future), contact tracing can be a very effective way to get people tested and isolated if they have been exposed to an infectious case, thereby limiting transmission. Contact tracing is most useful in the early stages of an outbreak, since the number of potential cases is small, and the outbreak may still be prevented or contained. With collective effort we may return to the point where each new case can be investigated as a local outbreak that can be prevented.” (Posted April 16, 2020)
“Contact tracing is useful because it allows us to help people at direct risk of infection, rather than only being able to act in ways that help the whole community, which helps us use broad actions like shelter-in-place more sparingly, and also ensures that we can direct our time and attention to where they’re needed most.” (Posted April 16, 2020)
“The benefits of contact tracing are, if done correctly, it is a thorough process that helps identify and quarantine exposed individuals so they cannot then transmit the virus to others; it breaks the chains of transmission.” (Posted April 16, 2020)
“Contact tracing is unique since it is part of the treatment, intervention and modeling of the COVID-19 pandemic. It helps find cases quickly to stay ahead of the disease and slow it down, to treat people early if necessary, and to inform us about the importance of our social networks.
“Epidemics are rarely maintained by the average individuals but often by superspreading events. Contact tracing helps us find out where and how frequently these happen, which is key in forecasting and controlling the spread of COVID-19.” (Posted April 16, 2020)
Are there special challenges to contact tracing of people who have been exposed to SARS-CoV-2?
“Contact tracing with Covid-19 is complicated by the low availability of testing, the rapidity of transmission and the likelihood that asymptomatic and pre-symptomatic cases may still transmit the disease. It is further complicated by staffing constraints during a widespread epidemic and the risks to investigators in high-prevalence communities. Another challenge is that this is a new disease – we are still learning about the hallmarks of infectiousness, the type of exposures, and the characteristics (like age or comorbidities) that put people at risk. Finally, the poor and inconsistent funding climate faced by our public health departments is a persistent national embarrassment; many health departments simply cannot afford staffing to conduct contact investigations. During unusual or high-risk outbreaks, the CDC will send teams of epidemiologists to aid in investigations, but in our current circumstances their resources have been stretched to their limits, and the CDC Director and others have recently proposed expanding these teams to help target these outbreaks in the U.S. Contact investigations are resource intensive, but as we are seeing they are highly cost-effective relative to the economic impact of an uncontrolled epidemic.” (Posted April 16, 2020)
“For COVID-19, it is almost certain to be the case that, on average, each infected individual whose contacts need to be traced will have more contacts than the average individual with an STD, so the workload will be substantial.” (Posted April 16, 2020)
“Respiratory diseases are always challenging for contact tracing because they can be spread to people you didn’t directly interact with, which makes the number of potential people we have to find much larger, and much harder for people to recall correctly. The long period of time people can be infected with SARS-CoV-2 without knowing they are infected or necessarily showing obvious symptoms makes this doubly challenging, as there’s also a much more vague time period we have to consider where people might have been exposed.” (Posted April 16, 2020)
“There are special challenges with COVID-19 contact tracing due to the incubation period, when a person may have been exposed to the virus, and the infectious period, when a person is infectious and could transmit the virus. A two-week period is a long period of time for people to recall how they may have been exposed. In addition, since a person can transmit the virus before having any symptoms, it makes it difficult for a person to remember who they may have exposed (their contacts). Also, since there are people who may never have signs and symptoms or have very minor signs and symptoms but can spread the virus, these individuals will likely not be identified in contact tracing and so the chains of transmission cannot be broken.” (Posted April 16, 2020)
How could technology facilitate COVID-19 contact tracing?
“Several mobile applications have been proposed to help notify individuals who have come into contact with infectious cases. Other apps might support contact notification in the spirit of partner notification, to help us inform those we may have exposed while also sharing this information with public health authorities. This would be useful in our current circumstances since we don’t have enough trained disease investigators to go around.
“Another kind of technology being explored for contact investigation uses “molecular epidemiology” to identify specific strains of a disease for more targeted investigations. This approach was pioneered in tuberculosis control but has since expanded to HIV, SARS, Ebola, and now Covid-19. However, the rate of transmission of the disease often outpaces the laboratory work, so new point-of-care testing and genotyping devices will be needed before this can be applied routinely.
“My own lab has done work in data visualization, geographic risk mapping, and informatics systems to help investigators transmit electronic data, link information from different sources, and recognize potential sources of high risk, such as a particular nursing home or church. Many groups are working hard to make this data flow efficiently from clinical and laboratory sources to public health so they can more efficiently identify those at risk through broader efforts to support disease surveillance and situational awareness.” (Posted April 16, 2020)
“First, technology helps facilitate contact tracing by allowing much of it to be done remotely, minimizing direct contact between public health workers and the people they are trying to help. But the use everyone is currently focusing on is the ability to use technology to try and identify people who someone came in contact with, even in locations they don’t remember being, or fleeting contacts they don’t remember having. That helps contact tracing be more thorough, and also helps reduce the strain on some very busy departments of health right now.” (Posted April 16, 2020)
“As manual contact tracing is so time and labor intensive, current technologies such as using cell phone signals and apps to identify and automate contact tracing may help supplement manual contact tracing efforts.” (Posted April 16, 2020)
“If privacy concerns can be addressed, technology should be able to be used to enhance and refine the process substantially, while the need to quarantine or isolate large numbers of individuals for up to 2 weeks would require more substantial resources.” (Posted April 16, 2020)
Are there privacy concerns related to contact tracing?
“Patient privacy is a top priority of public health authorities – there can be no investigations without trust, and therefore people can rely on public health agencies to protect their privacy. However, privacy is also a huge concern in the era of smartphones and digital tracking. Cell providers, marketing companies, and the government all have access to cell phone tower data that can localize mobile devices. This data has been used by some countries to guide their disease investigations. However, there are privacy-preserving approaches such as the Apple/Google partnership using opt-in Bluetooth data. There is a risk that this pandemic becomes a slippery slope that encourages more monitoring of the population for other purposes. Researchers and policy-makers alike should work with the public to identify which conditions are acceptable for the use of such information.” (Posted April 16, 2020)
“There are absolutely privacy concerns – you’re dealing with both people’s health information, and also data on where they’ve been and who they’ve seen. In order to do contact tracing properly, you have to know a lot about where someone was and who they were with at the time, and doing that on a massive, automated scale is absolutely a situation where a breach of privacy could very seriously impact the people you are trying to help.” (Posted April 16, 2020)
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Neil Abernethy, PhD, Associate Professor of Biomedical Informatics and Medical Education, University of Washington, said:
I have no conflicts with any of the above responses.
Eric Lofgren MSPH, PhD, Assistant Professor, Paul G. Allen School for Global Animal Health, Washington State University, said:
I’m funded by the CDC’s Modeling Infectious Diseases in Healthcare Network program.
Diana Cervantes, MS, DrPH, CPH, CIC, Assistant Professor at the University of North Texas Health Science Center at Fort Worth, Department of Biostatistics and Epidemiology and Director of the MPH Epidemiology Program, said:
I have no conflicts of interest to report.
Laurent Hébert-Dufresne, Assistant Professor, Vermont Complex Systems Center & Department of Computer Science, University of Vermont, said:
Arthur Reingold, MD, Professor of Epidemiology; Head, Division of Epidemiology and Biostatistics, School of Public Health, University of California, Berkeley, said:
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