Pathological evidence for residual SARS-CoV-2 in pulmonary tissues of a ready-for-discharge patient

1 May, 2020

SARS-CoV-2, a novel coronavirus and causing COVID-19, has given rise to a worldwide pandemic. So far, tens of thousands of COVID-19 patients have been clinically cured and discharged, but multiple COVID-19 cases showed SARS-CoV-2 positive again in discharged patients, which raises an attention for the dis- charged patients. Also, there is an urgent need to understand the pathogenesis of SARS-CoV-2 infection.

Here, you can read postmortem pathologic study in a ready-for- discharge COVID-19 patient who succumbed to sudden cardiovascular accident. Pathological examination revealed SARS- CoV-2-viruses remaining in pneumocytes and virus-caused pathological changes in the lungs. Our study provided new insights into SARS-CoV-2 pathogenesis and might facilitate the improvement of clinical guideline for virus containment and disease management.

Pathological features of COVID-19, especially in the pulmonary tissues of mild and recovering patients, remain largely unknown. In this study, the experts conducted postmortem study in an aged patient with mild COVID-19 pneumonia and found pathological changes of the lungs caused by SARS-CoV-2 infection. Histologically, they observed that the patient’s lung was predominated with diffuse alveolar damages, including disrupt of alveolar septa, proliferation and desquamation of type II AE, exudation of fibrin, monocytes and macrophages, and formation of hyaline membrane. These pulmonary pathologic features were consistent with those seen in SARS and Middle Eastern Respiratory Syndrome (MERS), highlighting that the successful methodology in managing SARS and MERS could be referred to COVID-2019 patients. By using comprehensive means including electron microscopy and IHC staining, they revealed remaining of SARS-CoV-2 in the lung from the ready-for-discharge patient, which raises a possibility that nasopharyngeal swab negative result might not reflect the virus in lung tissue. In addition, their work provided the first pathological evidence for residual virus in the lung for a patient with virus negative by nasopharyngeal swab—PCR test for consecutive three times. Therefore, PCR detection of SARS-CoV-2 nucleic acid on broncho-alveolar lavage fluid, extension of quarantine time, and the timely follow-up medical examination on discharged patients, especially aged ones with underlying diseases, were strongly recommended for dis- charged patients.

In this image, you can visualize a pathological observation of the lung tissues. Figure extracted from the original  article. 

a) Electron microscopic examination on a single pulmonary bronchiolar epithelial cell. Black arrows in left panel indicate organelle in pulmonary epithelial cell. Red arrows in right panel label virus particles. 

b) Electron microscopic examination on a single type II alveolar epithelial cell. Yellow arrow indicates organelle in pulmonary epithelial cell. Red arrows label virus particles. 

c) Immunohistochemical (IHC) staining of SARS-CoV-2 nucleoprotein (N) in pulmonary tissue with monoclonal anti-nucleoprotein antibody. The inset represents magnification of the selected area. Dark brown signals indicate positive staining for SARS-CoV-2 nucleoprotein and nuclei are counterstained with hematoxylin. 

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