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Transmission of 2019-nCoV Infection from an Asymptomatic Contact in Germany

Our take —

These early findings suggested that patients may be able to transmit the novel SARS-CoV-2 both before developing symptoms and after they stopped showing symptoms. Although the 5 cases in this case series were mild, they were hospitalized for infection control purposes. Given limited capacity of hospitals, infection control strategies will need to be managed alongside hospital demands during epidemic peaks. Furthermore, results suggested the potential importance of rapid contact tracing and testing of both symptomatic and asymptomatic contacts for epidemic control, as well as the potential need for prolonged isolation following recovery from suspected or confirmed COVID-19.

Study design

Case Series

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.

Study Strengths

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.

Limitations

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.

Value added

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.