SARS-CoV-2 in Body Fluids
Scientists from the National Institute for Viral Disease Control and Prevention in Beijing, China recently published their findings regarding the distribution of SARS-CoV-2 virus in different body fluids. Pharyngeal swabs were collected from most patients 1 to 3 days after hospital admission. Blood, feces, urine, sputum and nasal samples were collected throughout the admission. Bronchoalveolar lavage (BAL) fluid was collected from patients with severe illness who were ventilated.
SARS-CoV-2 RNA was detected in these samples by rRT-PCR. Cycle threshold values of rRT-PCR were used as indicators of the copy number of SARS-CoV-2 virus in specimens. A cycle threshold value less than 40 is interpreted as positive for SARS-CoV-2 RNA. Lower threshold values indicated higher viral copy numbers.
One thousand seventy specimens were collected from 205 patients with confirmed COVID19 disease. Ninety three percent of BAL specimens (14 of 15) were positive followed by 72% sputum (72 of 104), 63% nasal swabs (5 of 8), 32% pharyngeal swabs (126 of 398), 29% feces (44 of 153) and 1% of blood samples (3 of 307). None of 72 urine specimens tested positive. The average cycle threshold for all specimens was 31, which corresponded to a viral load of less than 2.6 x 104 copies per mL. Nasal swabs had a cycle threshold of 24, indicating a much higher viral load for 1.4 x 106 copies per mL.
Live virus was cultured from stool samples of 2 patients who did not have diarrhea. This finding indicates that SARS-CoV-2 may be transmitted by the fecal-oral route. The detection of viral RNA in 1% of blood samples may suggest systemic infection.
Reference
Wang W, et al. Detection of SARS-CoV-2 in Different Types of Clinical Specimens. JAMA published online March 11, 2020. doi:10.1001/jama.2020.3786.
