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Detectable serum SARS-CoV-2 viral load (RNAaemia) is closely correlated with drastically elevated interleukin 6 (IL-6) level in critically ill COVID-19 patients

Our take —

In a small study from Wuhan, China, the presence of virus in the blood was associated with severe inflammation and severe disease. Further study is needed to understand the temporal order of these findings and the potential prognostic value of detectable viremia.

Study design

Case Series

Study population and setting

The study included 48 patients with laboratory-confirmed SARS-CoV-2 infection admitted to a single hospital in Wuhan, China between February 1 and February 19, 2020 with moderate to critical illness (no mild cases). Pharyngeal and serum specimens were collected at the time of admission.

Summary of Main Findings

Viral RNA in the serum (RNAaemia) was detected in 10.4% (5/48) of patients. RNAaemia was present in 29% (5/17) of critically ill patients, but was not detected in moderate or severely ill patients. The presence of RNAaemia was associated with significantly higher levels of interleukin-6 (IL-6), which was itself correlated with disease severity.

Study Strengths

The study provided a detailed characterization of viral load and inflammatory markers.


The sample size was small, and all associations between biomarkers and disease severity did not account for possible confounding variables such as age and comorbidities. Further, because this study was cross-sectional, there was no assessment of whether RNAaemia preceded worsening disease and inflammation, or of any particular causal hypothesis.

Value added

This is one of the more in-depth studies to date of viremia and its association with inflammation.