Study population and setting
The study details the timeline and travel history of an index case traveling from Shanghai, China, to Munich, Germany, in January 2020, with pre-symptomatic COVID-19 infection, and the four cases in Germany resultant from that infection based on positive PCR testing.
Summary of Main Findings
A Chinese woman came to Munich for business meetings on January 20-21, 2020, with no signs or symptoms during her stay. She became ill on her flight back to China on January 22 and tested positive once she returned (Index patient). Contact tracing began upon notification on January 27. One of the index patient’s contacts in Munich, who had become ill just after meetings with his colleague from China, presented for assessment and had no visible symptoms at the time of testing and had not traveled outside Germany for 14 days, but tested positive for COVID-19 and was found to have a high viral load of 108 copies/mL in his sputum (Patient 1). A few days later, three additional employees at the company tested positive, one of which had contact with the index patient and the other two whom only had contact with Patient 1. Infection seems to have been transmitted during the incubation period of the index patient, and the detection of high sputum viral load in a patient who was recovering from symptoms warrants concern about prolonged shedding.
The potential exposures (business meetings), onset of symptoms, and positive tests among work colleagues happened during such a brief window of time (about 10 days), adding credibility to the findings. Availability of qRT-PCR testing on all four cases and further analysis of viral load on Patient 1 after recovery from symptoms are strengths of this study.
This was a case series with a small number of cases (5) and no information was provided related to the testing of other asymptomatic contacts. Nevertheless, contact tracing, clear links to the business traveler coming from a known hotspot, and careful documentation of the timing of events provided for valuable information.
This was one of the early studies providing evidence of transmission during the incubation period, along with viral shedding and therefore potential transmission after presumed recovery.