Viral load of SARS-CoV-2 in clinical samples
Authors: Yang Pan, Daitao Zhang, Peng Yang, Leo L M Poon, Quanyi Wang
Journal: The Lancet Infectious Diseases (2020)

An outbreak caused by a novel human coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was first detected in Wuhan in December 2019,1Lu R Zhao X Li J et al.Genomic characterisation and epidemiology of 2019 novel coronavirus: implications for virus origins and receptor binding.Lancet. 2020; (published online Jan 30.)https://doi.org/10.1016/S0140-6736(20)30251-8Summary Full Text Full Text PDF Scopus (8212) Google Scholar and has since spread within China and to other countries. Real-time RT-PCR assays are recommended for diagnosis of SARS-CoV-2 infection.2WHOLaboratory testing for 2019 novel coronavirus (2019-nCoV) in suspected human cases. Interim guidance.https://www.who.int/publications-detail/laboratory-testing-for-2019-novel-coronavirus-in-suspected-human-cases-20200117Date: Jan 17, 2020Date accessed: February 11, 2020Google Scholar However, viral dynamics in infected patients are still yet to be fully determined. Here, we report our findings from different types of clinical specimens collected from 82 infected individuals. Serial samples (throat swabs, sputum, urine, and stool) from two patients in Beijing were collected daily after their hospitalisation (patient 1, days 3–12 post-onset; patient 2, days 4–15 post-onset). These samples were examined by an N-gene-specific quantitative RT-PCR assay, as described elsewhere.3Chu DKW Pan Y Cheng SMS et al.Molecular diagnosis of a novel coronavirus (2019-nCoV) causing an outbreak of pneumonia.Clin Chem. 2020; (published online Jan 31.)DOI:10.1093/clinchem/hvaa029Crossref PubMed Scopus (941) Google Scholar The viral loads in throat swab and sputum samples peaked at around 5–6 days after symptom onset, ranging from around 104 to 107 copies per mL during this time (figure A, B). This pattern of changes in viral load is distinct from the one observed in patients with SARS, which normally peaked at around 10 days after onset.4Peiris JS Chu CM Cheng VC et al.Clinical progression and viral load in a community outbreak of coronavirus-associated SARS pneumonia: a prospective study.Lancet. 2003; 361: 1767-1772Summary Full Text Full Text PDF PubMed Scopus (1986) Google Scholar Sputum samples generally showed higher viral loads than throat swab samples. No viral RNA was detected in urine or stool samples from these two patients. We also studied respiratory samples (nasal [n=1] and throat swabs [n=67], and sputum [n=42]) collected from 80 individuals at different stages of infection. The viral loads ranged from 641 copies per mL to 1·34 × 1011 copies per mL, with a median of 7·99 × 104 in throat samples and 7·52 × 105 in sputum samples (figure C). The only nasal swab tested in this study (taken on day 3 post-onset) showed a viral load of 1·69 × 105 copies per mL. Overall, the viral load early after onset was high (>1 × 106 copies per mL). However, a sputum sample collected on day 8 post-onset from a patient who died had a very high viral load (1·34 × 1011 copies per mL). Notably, two individuals, who were under active surveillance because of a history of exposure to SARS-CoV-2-infected patients showed positive results on RT-PCR a day before onset, suggesting that infected individuals can be infectious before them become symptomatic. Among the 30 pairs of throat swab and sputum samples available, viral loads were significantly correlated between the two sample types for days 1–3 (R2=0·50, p=0·022), days 4–7 (R2=0·93, p<0·001), and days 7–14 (R2=0·95, p=0·028). From 17 confirmed cases of SARS-CoV-2 infection with available data (representing days 0–13 after onset), stool samples from nine (53%; days 0–11 after onset) were positive on RT-PCR analysis. Although the viral loads were less than those of respiratory samples (range 550 copies per mL to 1·21 × 105 copies per mL), precautionary measures should be considered when handling faecal samples. We declare no competing interests. This work was supported by the Theme-based Research Scheme (UGC, Hong Kong). Genomic characterisation and epidemiology of 2019 novel coronavirus: implications for virus origins and receptor binding2019-nCoV is sufficiently divergent from SARS-CoV to be considered a new human-infecting betacoronavirus. Although our phylogenetic analysis suggests that bats might be the original host of this virus, an animal sold at the seafood market in Wuhan might represent an intermediate host facilitating the emergence of the virus in humans. Importantly, structural analysis suggests that 2019-nCoV might be able to bind to the angiotensin-converting enzyme 2 receptor in humans. The future evolution, adaptation, and spread of this virus warrant urgent investigation. Full-Text PDF Viral dynamics in mild and severe cases of COVID-19Coronavirus disease 2019 (COVID-19) is a new pandemic disease. We previously reported that the viral load of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) peaks within the first week of disease onset.1,2 Findings from Feb, 2020, indicated that the clinical spectrum of this disease can be very heterogeneous.3 Here, we report the viral RNA shedding patterns observed in patients with mild and severe COVID-19. Full-Text PDF Stability of SARS-CoV-2 in different environmental conditionsWe previously reported the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in different clinical samples.1 This virus can be detected on different surfaces in a contaminated site.2 Here, we report the stability of SARS-CoV-2 in different environmental conditions. Full-Text PDF Open Access