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Evidence of SARS-CoV-2 RNA in an Oropharyngeal Swab Specimen, Milan, Italy, Early December 2019

Our take —

The study sought to examine whether SARS-CoV-2 infections occurred in archived oropharyngeal samples from the Measles and Rubella network obtained from September to December 2019. They found one sample tested positive obtained December 5, 2019, from a 4-year-old boy who did not report a history of travel. While there may be some sample quality issues that biased findings towards the null in other samples, this finding suggests that SARS-CoV-2 was circulating in the population months before the first reported clinical case on February 21, 2020.

Study design

Case Series

Study population and setting

In order to better understand when SARS-CoV-2 infections first spread to Italy, patients identified through the Measles and Rubella Network and suspected of having measles but testing negative for measles during September 2019 to February 2020 were included in the study. Oropharyngeal swabs from 39 patients were tested for SARS-CoV-2 RNA using an in-house PCR assay for the SARS-CoV-2 spike protein.

Summary of Main Findings

Patients tested ranged in age from 8 months to 73 years with a mean of 19.9 years. From these 39 samples, one swab tested positive in a 4-year-old boy who resided nearby Milan with no reported travel history. On November 21, 2020, the child began have symptoms of cough and rhinitis. On November 30, the child developed respiratory symptoms and vomiting which developed into a measles-like rash on December 1. The swab was obtained on December 5, 14 days after symptom onset.

Study Strengths

The study strength was in the use of archived samples with detailed clinical and travel history. In addition, the partial viral sequence recovered from the one positive sample provides further confidence in the validity of the PCR result.

Limitations

The study limitations are the length of time since the samples were collected, as degradation may have occurred in these samples which would bias the study toward null findings, and type of specimen collected from patients – oropharyngeal swabs – which are suboptimal for SARS-CoV-2 testing. Additionally, similar to the patient who had a positive swab, other patients may have had delays between symptom onset and sample collection, again biasing toward null findings. Finally, the study was not able to recover a full length genome sequence from the positive sample, precluding interpretations of the origin of the infecting virus.

Value added

This study shows that SARS-CoV-2 infections were occurring in Italy nearly 3 months before the first reported case on February 21, 2020.

This review was posted on: 22 January 2021