Travel-Related Cases of SARS-CoV-2 in America.

Travel-Related Cases of SARS-CoV-2 in America. Spencer EA, Heneghan C.

Published on June 27, 2020

Reference Burke et al. Enhanced Contact Investigations for Nine Early Travel-Related Cases of SARS-CoV-2 in the United States. medRxiv 2020.04.27.20081901; doi:
Study type
Country USA
Setting Household, community
Funding Details Non Reported
Transmission mode Close contact, Person to person, Fomite
Exposures Person to Person

Bottom Line

No transmission among non-household contacts was detected. Among 15 household contacts, only 2 secondary cases (each the spouse of the respective case) were detected.

Evidence Summary

553 close contacts of nine travel-associated COVID-19 cases were identified, and a convenience sample of 404 was actively monitored.

Across all known close contacts under monitoring, two additional cases were identified; both secondary cases were in spouses of travel-associated case-patients.

The secondary attack rate among household members, all of whom had ≥1 respiratory sample tested, was 13% (95% CI: 4 to 38%).

No secondary infections were detected among household members who were cohabiting with their confirmed SARS-CoV-2-positive household members during the period of case isolation.

No symptomatic secondary cases of COVID-19 among the 389 non-household contacts who completed active monitoring.

“For community contacts exposed in the healthcare setting…..Of those with data, many reported having face-to-face contact (27/35; 77%) with the travel-associated case patient or spending time within 6 feet of the patient (34/38; 90%), and nearly all (43/45; 96%) could remember being in the same room as the travel-associated case-patient. Fewer (8/28; 29%) reported being within 6 feet of the patient while the patient was coughing.”

No community contacts were subsequently diagnosed with COVID-19.

What did they do?

Close contacts of nine early travel-related cases in the United States were identified.

Close contacts meeting criteria for active monitoring were followed, and selected individuals were targeted for collection of additional exposure details and respiratory samples.

Enhanced contact investigations were conducted with the 9 cases, and included in-depth interviews to better characterize exposure type, exposure duration, and contact medical history, in addition to the collection of respiratory specimens to identify asymptomatic or pre-symptomatic infections.

Respiratory samples were tested for SARS-CoV-2 by real-time reverse transcription-polymerase chain reaction (RT-PCR) at the Centers for Disease Control and Prevention.

Study reliability

The sample was a convenience sample: “the selection of the sample for interview and respiratory specimen collection was not systematic or consistent across sites. This may have introduced bias in the characteristics of the close contacts described as well as in the secondary attack rates.”

The procedures used were heterogeneous across sites as different teams made different decisions regarding the definition of close contacts, and which exposure information to collect.

Secondary transmissions occurring prior to symptom onset in the travel-associated case-patient may have been missed. 

Clearly defined setting Demographic characteristics described Follow-up length was sufficient Transmission outcomes assessed Main biases are taken into consideration
Yes No Yes Partly * No
* Only 47% of actively monitored close contacts provided any respiratory specimens

What else should I consider?

“It is possible that asymptomatic secondary cases could have developed in persons from whom respiratory samples were not collected, or that secondary cases could have developed without being detected in respiratory samples (for instance, if the timing of shedding did not align with the timing of sample collection)”

About the authors

Carl Heneghan

Carl is Professor of EBM & Director of CEBM at the University of Oxford. He is also a GP and tweets @carlheneghan. He has an active interest in discovering the truth behind health research findings

Elizabeth Spencer

Dr Elizabeth Spencer; MMedSci, PhD. Epidemiologist, Nuffield Department for Primary Care Health Sciences, University of Oxford.