Detection of SARS-CoV-2 RNA in Stool Samples

Research Findings from China

Investigators in China have successfully identified SARS-CoV-2 RNA in stool samples from patients, indicating that the virus can replicate and be released through the digestive system. Notably, the virus was found in 23.92% of cases even after it had cleared from the respiratory tract.

Spike Proteins and Viral Entry

Similar to how rock climbers depend on climbing picks for survival, coronaviruses rely on spike proteins, or transmembrane S-glycoproteins, to enter human cells. These spike proteins are responsible for the virus’s characteristic crown-like appearance. They attach to a human cell membrane protein known as angiotensin-converting enzyme 2 (ACE2), which plays a crucial role in regulating cardiovascular and renal functions. Following this attachment, the viral genome (RNA) is introduced into the host cell, where it hijacks the cell’s machinery to produce new viral components. This process results in the assembly and release of new virions, which can then infect other cells with ACE2 receptors.

Symptoms Associated with Infection

SARS-CoV-2 primarily targets human airway ACE2 proteins, making them vulnerable to the virus present in respiratory droplets from coughing and sneezing. Common respiratory symptoms include fever, dry cough, labored breathing, and varying degrees of pneumonia. Interestingly, patients may also experience gastrointestinal symptoms such as diarrhea, nausea, vomiting, and abdominal discomfort prior to the onset of respiratory symptoms.

Previous Research and New Evidence

Prior studies on SARS have shown the ability to detect viral content in stool samples. In two recent papers published in Gastroenterology, researchers from Wuhan, China, confirmed the presence of SARS-CoV-2 RNA in stool samples of infected patients. Out of 73 hospitalized patients, 53.42% tested positive for the virus in their stool samples, with positive results lasting from one to 12 days.

An endoscopy performed on one of the patients revealed the presence of ACE2 proteins in gastrointestinal epithelial cells, supporting the hypothesis of new virion assembly released through the gastrointestinal tract. Notably, the first COVID-19 patient in the United States reported symptoms of nausea and vomiting two days prior to hospitalization, and loose stools tested positive for viral RNA.

Understanding Gastrointestinal Symptoms

Recent bioinformatics analyses indicate that ACE2 proteins are not only highly expressed in the lungs but also in the gastrointestinal system. However, the precise mechanism behind gastrointestinal symptoms is still not entirely understood.

Recommendations and Precautions

According to the current China Disease Control and Prevention guidelines, transmission-based precautions should be maintained for hospitalized patients until they test negative for SARS-CoV-2 in at least two sequential respiratory tract specimens collected 24 hours apart. Given that 23.29% of patients exhibited positive stool samples even after respiratory viral clearance, researchers recommend routine testing for SARS-CoV-2 in the feces of infected or suspected individuals. They also suggest that patients should not be discharged from the hospital if their fecal tests remain positive.

Another significant concern is the potential for viral transmission via fecal-oral contamination. To mitigate this risk, enhanced bathroom hygiene practices should be implemented. Clinicians are also advised to remain vigilant in identifying patients who present with initial gastrointestinal symptoms, which could lead to earlier diagnosis, isolation, and treatment.

References

– AmerGastroAssn. (n.d.). GI symptoms and potential fecal transmission in coronavirus patients. Retrieved from https://www.eurekalert.org/pub_releases/2020-03/aga-gsa030520.php
– Gu J, Han B, Wang J. COVID-19: Gastrointestinal manifestations and potential fecal-oral transmission, Gastroenterology (2020).
– Xiao F, Tang M, Zheng X, Liu Y, Li X, Shan H. Evidence for gastrointestinal infection of SARS-CoV-2, Gastroenterology (2020). doi: https://doi.org/10.1053/j.gastro.2020.02.055
– Chris, Thomas, & C., M. (2012, March 20). Angiotensin-Converting Enzyme 2 (ACE2) Is a Key Modulator of the Renin Angiotensin System in Health and Disease. Retrieved from https://www.hindawi.com/journals/ijpep/2012/256294/