Spread of COVID-19 and Effectiveness of Contact Tracing in a University Population


To control the spread of any infectious disease, including coronavirus disease 2019 (COVID-19), contact tracing is a valuable tool. Contact tracing is used to identify people at high risk of infection due to contact with someone known to be infected, and then testing, treating (if necessary), or counseling them to self-isolate to prevent further infection. further spread of the disease. Typically, contact tracing is used for sexually transmitted infections, where the definition of contact is clearly established.

Study: Limited impact of contact tracing in an academic setting for COVID-19 due to asymptomatic transmission and social distancing. Image Credit: Tikhonova Yana / Shutterstock

The Social Contact Survey (SCS) formulated mathematical modeling to assess infectious diseases from data collected on patterns of social contact for the general UK population in 2010. However, academic populations differ in many ways from the general population. Students are generally younger adults with a higher than average number of social contacts and tend to live in shared residences. Additionally, due to restrictions imposed during the COVID-19 pandemic, the way people socialize has changed dramatically. In June 2020, the Coronavirus Questionnaire (CON-QUEST) was launched to capture any new pattern of contact among academic staff and students during the pandemic.

Using these two surveys, a group of researchers from the University of Bristol were able to study how the social behaviors of an academic population changed with social restrictions and then the effectiveness of contact tracing in such a framework. The effectiveness of contact tracing is assessed by its ability to limit the extent of the spread of the disease by an infected person and the ability of the program to trace and discover asymptomatic index cases.

A pre-printed version of this study, which is yet to be peer reviewed, is available on the website medRxiv * server.

The study

The CON-QUEST survey reported a median number of daily contacts of a value of two, compared to nine for the college-affiliated subset of CBS. The number of respondents with low amounts of daily contact was higher in CON-QUEST data compared to SCS data. The number of respondents who reported one, two or three contacts per day is an order of magnitude higher in the CON-QUEST data compared to the data in the SCS subset. In the SCS subset data, the maximum number of daily contacts was greater than that in the CON-QUEST data. There was also a higher overall number of respondents with a high number of contacts in the SCS subset.

Compared to data collected in 2010, the duration of social contacts reported in 2020 has increased. The interactions of those in the CON-Quest survey lasted longer than those in the SCS survey. In addition to the longer duration of social contact, those in the CON-QUEST survey also reported more frequent contact compared to those in the SCS survey. People in the CON-QUEST survey reported a greater number of “eight or more times” contact opportunities than those in the SCS survey.

In an academic population, the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections appears to depend on the infectivity of the index case, the rate of transmission and the implementation of research. contacts. Data indicates that an increase in the rate of transmission always leads to an increase in the average number of secondary cases. Without contact tracing, symptomatic index cases lead to an increase in the number of secondary cases compared to asymptomatic index cases due to their greater infectivity.

However, when contact tracing is implemented, the spread of COVID-19 from symptomatic index cases is significantly reduced. Although contact tracing appears to have minimal effect on reducing asymptomatic index cases. With symptomatic index cases, contact tracing can potentially reduce the average number of secondary cases by up to 56%, with the greatest impact being lower transmission rates.


This study compared the results of an investigation conducted before the pandemic and an investigation conducted during the pandemic by examining the duration, frequency and number of contacts reported in each investigation. From the available data, the authors built a self-centered network to model the actual transmission of COVID-19 from index cases to people they meet. Contact tracing was then introduced to study three scenarios in which the index case was always symptomatic, always asymptomatic, or asymptomatic with an age-dependent probability.

During the period of government-imposed restriction on social gatherings, patterns of contact among university populations changed. Individuals generally encountered less contact for long periods and with increased frequency. Due to these behavioral changes, reductions in the average number of secondary infections were observed. University populations are expected to have a high incidence of asymptomatic cases, so in cases like this, mass testing is needed to identify asymptomatic individuals and make full use of contact tracing.

*Important Notice

medRxiv publishes preliminary scientific reports which are not peer reviewed and, therefore, should not be considered conclusive, guide clinical practice / health-related behavior, or treated as established information.


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