Investigation of a COVID-19 outbreak in Germany resulting from a single travel-associated case

Investigation of a COVID-19 outbreak in Germany resulting from a single travel-associated case. Spencer EA, Heneghan C

Published on July 23, 2020

Reference Böhmer MM, Buchholz U, Corman VM, et al. Investigation of a COVID-19 outbreak in Germany resulting from a single travel-associated primary case: a case series.  Lancet Infect Dis. 2020;S1473-3099(20)30314-5.  2020
Study type
Country Germany
Setting Community
Funding Details All authors are employed and all expenses covered by governmental, federal state, or other publicly funded institutions.
Transmission mode Person to person, Close contact
Exposures Travel, Household

Bottom Line

Cases in this study in Bavaria, Germany presented with predominately mild, non-specific symptoms. Infectiousness before or on the day of symptom onset was substantial. The incubation period was often short and false-negative tests occurred.

Evidence Summary

Patient zero was a Chinese resident who visited Germany for professional reasons. Sixteen  subsequent cases, often with mild and non-specific symptoms, emerged in four transmission generations. 

Signature mutations in the viral genome occurred upon foundation of generation two, as well as in one case pertaining to generation four. 

Transmission events were likely to have occurred presymptomatically for one case (possibly five more), at the day of symptom onset for four cases (possibly five more), and the remainder after the day of symptom onset or unknown. 

One or two cases resulted from contact with a case during the prodromal phase.

Secondary attack rates were 3/4 among members of a household cluster in common isolation, 2/20 among household contacts only together until isolation of the patient, and 11/217 (5·1%, 95% CI, 2·6% to 8·9%) among non-household, high-risk contacts.

What did they do?

An outbreak in Bavaria, Germany, starting at the end of January 2020, was studied for transmission events, incubation period, and secondary attack rates. 

Case interviews were done to describe timing of onset and nature of symptoms and to identify and classify contacts as high risk (had cumulative face-to-face contact with a confirmed case for ≥15 min, direct contact with secretions or body fluids of a patient with confirmed COVID-19, or, in the case of health-care workers, had worked within 2 m of a patient with confirmed COVID-19 without personal protective equipment) or low risk (all other contacts). 

High-risk contacts were ordered to quarantine for 14 days and were actively followed up and monitored for symptoms; low-risk contacts were tested upon self-reporting of symptoms. 

Whole genome sequencing confirmed epidemiological links and transmission events where contact histories were ambiguous.

Study reliability

This was a detailed study of transmission among a satellite outbreak in Germany. It was not possible to identify all relevant contacts.  We could not find the reported  total numbers of individuals traced as being contacts (high and low risk) in the main paper.

Clearly defined setting Demographic characteristics described Follow-up length was sufficient Transmission outcomes assessed Main biases are taken into consideration
Yes Yes Yes Yes Unclear

What else should I consider?

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.