High Fecal Viral Levels Found in COVID-19 Disease and in Asymptomatic Carriers
SARS-CoV-2, the virus that causes COVID-19, can be detected in the stool of up to 53.4% of COVID-19 patients.2-6 In about 23% of cases, patients were no longer positive for the virus in respiratory samples, yet stool samples were still positive,2 clearly underlining the value of fecal testing. Data from 98 COVID-19 patients showed viral shedding in stool for nearly five weeks after respiratory samples were negative.1 Another study reported that patients shed the virus in stool 30 days after initial infection.7 Even asymptomatic carriers may show elevated SARS-CoV-2 in stool.5 Therefore, Wu and colleagues recommend routine RT-PCR stool testing to determine when it is safe to discontinue precautions in recovered COVID-19 patients, so as to prevent transmission of the virus and best allocate medical resources.1
A Direct Link Between COVID-19 and Gastrointestinal Illness
SARS-CoV-2 gains entry into the host via the ACE2 protein, which is found not only in lung epithelia, but also gut epithelia. Therefore, the gut could present an entryway into the host and may be a site of viral infection.7 Indeed, two to eighteen percent of patients with COVID-19 had diarrhea, abdominal pain, and vomiting.7,8 Ten percent of patients presented with diarrhea and nausea one to two days before they developed fever and respiratory symptoms.2-6 And in some cases, digestive symptoms were the primary symptom of COVID-19.7 Further, GI symptoms with COVID-19 may indicate a more severe course of illness.7 For example, abdominal pain was reported more frequently in patients admitted to the intensive care unit.6 SARS-CoV-2 can also be detected in fecal specimens of asymptomatic patients.
Identify and Prevent Potential Fecal-Oral Transmission of COVID-19
The presence of SARS-CoV-2 in stool points to a potential fecal-oral transmission route for COVID-19.9 Asymptomatic individuals could therefore spread SARS-CoV-2 unknowingly, although this still remains to be proven. Potential fecal-oral transmission of COVID-19 presents risks for medical personnel having contact with patient stool. Additionally, endoscopic procedures could facilitate the transmission of SARS-CoV-2 through exposure to the virus in gastrointestinal tissues or mucus.10
The Gut-Lung Axis
The gut microbiome may have a role in lung health. In respiratory tract infections, pathogens invade the airways and multiply. Infection depends on the number and virulence of pathogens, but perhaps more importantly – the host’s defenses.11 Acute respiratory infections such as influenza can initiate dysbiosis in the respiratory and gastrointestinal tracts, which may promote the development of secondary bacterial pneumonias.12 In some studies, oral probiotics have shown protective effects against influenza virus, pneumococcal infections, and ventilator-induced pneumonia.11 This points to a possible strategy of improving the gut microbiome to improve immune defenses and prevent respiratory infections.