The detection of SARS-CoV-2 genetic material in human feces, often called “COVID poop,” indicates infection. This viral RNA in stool offers insights into the virus’s spread within individuals and communities.
The Virus in Your Gut and Feces
SARS-CoV-2, the virus causing COVID-19, can infect cells within the gastrointestinal (GI) tract. It uses the angiotensin-converting enzyme 2 (ACE2) receptor, widely present on digestive system cells, to enter and replicate. This replication contributes to its detection in fecal matter.
Many individuals with COVID-19 experience GI symptoms, including diarrhea, nausea, vomiting, and abdominal pain. Studies report diarrhea in approximately 8.4% to 12% of adult cases and nausea in about 4.1%.
Infected individuals shed viral RNA in feces, even if they are asymptomatic or do not experience GI symptoms. Viral shedding in feces can begin before, during, or after the onset of respiratory symptoms. The abundance of viral genetic material in feces typically ranges from 10^2 to 10^7 gene copies per milliliter, which is lower than in nasopharyngeal fluids, but still detectable.
Community Monitoring Through Wastewater
Wastewater surveillance, also known as wastewater epidemiology, involves collecting samples from sewage systems to test for SARS-CoV-2 RNA. This non-invasive method monitors the virus at a community level, reflecting shedding from both symptomatic and asymptomatic individuals. Samples are typically collected from wastewater treatment plants, offering a broad snapshot of infection trends.
Wastewater surveillance data acts as an early warning signal for community-level outbreaks. It can detect changes in infection trends approximately four to six days before these changes are reflected in clinical case reports. This early detection allows public health officials to anticipate surges, identify emerging hotspots, and track the prevalence of different SARS-CoV-2 variants.
The process involves extracting and concentrating SARS-CoV-2 RNA from wastewater, followed by molecular and genomic tools to identify, quantify, and characterize the virus. This cost-effective approach does not rely on individual clinical testing, providing a comprehensive view of community infection dynamics. By complementing traditional clinical surveillance, wastewater data helps inform public health decisions, such as resource allocation for testing sites or vaccination clinics.
Understanding Transmission Risk
While SARS-CoV-2 RNA is detectable in feces, “COVID poop” is not a significant source of COVID-19 transmission. Infectious virus particles are rarely found in stool samples, and if present, are typically in very low concentrations. This suggests the detected genetic material is often fragmented and not capable of causing infection.
The primary mode of SARS-CoV-2 transmission remains through respiratory droplets and aerosols expelled when an infected person coughs, sneezes, breathes, talks, or sings. Direct person-to-person contact and exposure to contaminated surfaces also play a role in spreading the virus. The risk of fecal-oral transmission for COVID-19 is considered very low.
Experimental studies have shown it is possible to infect cell cultures, organoids, and animals with SARS-CoV-2 derived from feces, but strong epidemiological evidence supporting human fecal-oral transmission is limited. Therefore, while general hygiene practices like thorough handwashing remain important for overall health and preventing the spread of many infectious diseases, this is not specifically driven by a significant risk of COVID-19 fecal transmission.
How Long Does the Virus Linger in Poop?
SARS-CoV-2 RNA shedding in feces can persist for an extended period after the initial infection. Studies have shown that viral RNA can be detected in stool for weeks and even months after respiratory symptoms have resolved or after an individual tests negative via a nasal swab. For instance, approximately half of individuals with mild to moderate COVID-19 shed viral genetic material in their feces within a week of diagnosis, with about 13% still shedding at four months, and nearly 4% at seven months post-infection.
The median duration of detectable viral RNA in stool has been estimated at around 17 to 26 days from symptom onset, with some reports indicating shedding for up to 12 weeks or more. The prolonged presence of viral RNA in feces does not necessarily mean the individual is still infectious, as the detected RNA might be from non-viable viral fragments. However, this extended shedding period is particularly relevant for wastewater surveillance, as it provides a sustained signal of community infection, even as individual clinical cases decline or resolve.