Close contact and risk of SARs-CoV-2 infection
Close contact and risk of SARs-CoV-2 infection. Spencer EA, Jefferson T, Heneghan C.
https://www.cebm.net/study/covid-19-close-contact-and-risk-of-sars-cov-2-infection/
Published on June 22, 2020
Included in
Transmission Dynamics of COVID-19
| Reference |
Liu Y, Eggo RM, Kucharski AJ. Secondary attack rate and superspreading events for SARS-CoV-2. Lancet. 2020;395(10227):e47 |
| Study type |
|
| Country |
China and France |
| Setting |
Specific events associated with transmission such as a family gathering. |
| Funding Details |
Non reported |
| Transmission mode |
Close contact, person to person |
| Exposures |
Household contacts, gatherings, shared accomadation |
Bottom Line
In transmission events, after sharing a meal or staying at a chalet the secondary attack rate is estimated as very high.
Evidence Summary
In transmission events, after sharing a meal or staying at a chalet the secondary attack rate is estimated as very high at around 35%. There is variation between these nine events.
| Setting |
The number at the gathering (excluding indeed case) |
Number infected |
| Meal (homeΩ0 |
8 |
8 (100%) |
| Meal (home) |
13 |
4 (31%) |
| Meal (unknown) |
1 |
1 (100%) |
| Meal (unknown) |
14 |
3(21%) |
| Meal (restaurant) |
14 |
3 (21%) |
| Meal (unknown) |
17 |
2 (12%) |
| Meal (unknown) |
47 |
10(21%) |
| Chalet |
11 |
5 |
| Meal |
18 |
8 |
What did they do?
This is a journal letter and the full details of the methods can not be obtained. The authors estimated the secondary attack rate from a number of cases in Wuhan, up until 27th February 2020.
Study reliability
This is an early estimate of transmission from one location early in the pandemic so is unlikely to reflect a wider context and is unlikely to be reproducible. This is a small study. The time duration of exposure is not investigated here but is likely to impact transmission in different contexts. The authors note that reports at that time may have been biased towards larger transmission events. There is also an assumption that all the secondary infections were generated by a single primary case.
| Clearly defined setting |
Demographic characteristics described |
Follow-up length was sufficient |
Transmission outcomes assessed |
Main biases are taken into consideration |
|
Unclear |
No |
Unclear |
Yes
|
No |
What else should I consider?
The authors point out that “if it transpires that most at-risk contacts have a close relationship with cases, and superspreading events tend to occur at large gatherings of these close contacts, measures to reduce infection risk during such gatherings and subsequent tracing of close contacts of cases might have a disproportionate effect on reducing overall transmission.”
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.
Tom Jefferson
Tom Jefferson, epidemiologist.
