Covid-19, caused by the SARS-CoV-2 virus, has affected millions of people globally since its emergence in late 2019. The most common symptoms of Covid-19 include fever, cough, fatigue, headache, and loss of taste or smell. However, there have been reports of gastrointestinal symptoms like diarrhea occurring in some Covid-19 patients. This has led to questions around whether diarrhea is a definitive symptom of Covid-19 that occurs in all cases.
Prevalence of Diarrhea in Covid-19
Multiple studies have analyzed the frequency of gastrointestinal symptoms, including diarrhea, in Covid-19 patients. A meta-analysis published in August 2020 looked at over 4500 Covid-19 patients across 36 studies. It found the overall prevalence of diarrhea among Covid-19 patients to be about 7.7% (1). However, prevalence ranged quite a bit across the different studies, from 2% to 49.5%.
Some other analyses on the frequency of diarrhea in Covid-19 include:
– A study in China looking at 204 hospitalized Covid-19 patients found 10.3% had diarrhea (2).
– A study in the USA on 116 hospitalized Covid-19 patients found 31.9% had diarrhea (3).
– A study in China on 73 hospitalized patients with mild Covid-19 found diarrhea in only 3% (4).
The wide variation in reported prevalence reinforces that not all Covid-19 patients experience diarrhea. Multiple factors likely impact an individual’s chance of having gastrointestinal manifestations.
Risk Factors for Covid-19 Diarrhea
Researchers have tried to identify factors that increase the risk of diarrhea in Covid-19. Some patterns have emerged:
– **Severity of illness** – Multiple studies have found higher rates of diarrhea in patients with more severe Covid-19 that requires hospitalization compared to mild cases (5, 6). One study found diarrhea in up to 50% of critical cases (7). The virus likely causes more extensive gastrointestinal infection and inflammation in severe Covid-19.
– **Demographics** – Some studies have found higher rates of diarrhea in younger Covid-19 patients compared to older individuals (8). One study in China found Covid-19 patients under the age of 60 had diarrhea more often than those over 60 (9). The reasons for this association require more research.
– **Medications** – Some therapeutic medications used in hospitalized Covid-19 cases, like antibiotics, can also cause diarrhea as a side effect (10).
– **Possibly individual susceptibility** – Not all studies have found associations between diarrhea and factors like age or disease severity (11). This suggests some individuals may simply be more prone to gastrointestinal manifestations than others when they get Covid-19.
More research is needed to clarify which patients are at highest risk of developing diarrhea from Covid-19. But current evidence shows not every individual has the same likelihood of experiencing this gastrointestinal symptom.
Possible Mechanisms of Diarrhea in Covid-19
There are several ways SARS-CoV-2, the virus that causes Covid-19, could result in diarrhea:
– **Direct infection of the gastrointestinal tract** – SARS-CoV-2 can directly infect and replicate in the cells of the intestinal tract (12). Infection likely causes inflammation and dysfunction, resulting in symptoms like diarrhea.
– **Systemic infection** – Severe Covid-19 often causes system-wide inflammation. This exaggerated immune response may extend to the gastrointestinal tract and cause diarrhea.
– **Medication side effects** – As mentioned above, some therapeutics used in hospitalized patients like antibiotics can have diarrhea as an adverse effect.
– **Changes in gut microbes** – Emerging research suggests SARS-CoV-2 infection may disrupt the balance of bacteria and other microbes in the intestines (13). This “dysbiosis” has been associated with diarrhea in other gastrointestinal conditions.
– **Exaggerated neurological signaling** – The vagus nerve helps control intestinal function. Some scientists speculate SARS-CoV-2 could impair signaling along this nerve, leading to abnormal gastrointestinal activity (14). But more research is needed in this area.
The gastrointestinal tract is clearly susceptible to the effects of SARS-CoV-2 infection. But the virus may not impact the intestines and cause diarrhea in the same way in every patient.
Is Diarrhea a Defining Symptom of Covid-19?
Based on the currently available information, diarrhea does not appear to be a defining universal symptom of Covid-19. Here is some perspective:
– Diarrhea occurs in only a minority of Covid-19 cases. Meta-analyses show the average rate is under 10%, although some studies have reported higher frequencies.
– Many other common symptoms like fever, cough, and fatigue occur far more often in Covid-19 patients. These seem to be more consistent hallmarks of infection.
– People with other respiratory infections, such as seasonal influenza, can also develop diarrhea (15). It is not a symptom specific to Covid-19.
– A significant portion of infected individuals have completely asymptomatic Covid-19 infections, with no symptoms at all (16). Diarrhea clearly does not happen in these cases.
So in summary, while diarrhea can certainly accompany Covid-19, current evidence suggests it is not a defining feature of infection like cough or sudden loss of smell. It may simply be a secondary symptom that manifests in some patients due to the effects of the virus on the gastrointestinal system or medications. But many infected individuals never experience diarrhea.
Should Diarrhea Prompt Covid-19 Testing?
Because diarrhea appears to be an inconsistent, secondary symptom of Covid-19, experiencing diarrhea on its own may not be enough to warrant Covid-19 testing. However, there are some situations where new-onset diarrhea should prompt suspicion of possible Covid-19:
– You have other symptoms suggestive of Covid-19 like fever, cough, or sudden loss of taste/smell. Diarrhea in combination with these primary symptoms increases the probability of possible Covid-19.
– You have a known or suspected exposure to someone with Covid-19.
– You have recently traveled to an area with active spread of Covid-19.
– You have not been fully vaccinated against Covid-19.
– Diarrhea is persisting longer than 48 hours or is accompanied by symptoms like bloody stool, intense abdominal pain, dehydration, or fever, indicating a more serious gastrointestinal problem that requires medical assessment.
Unless the diarrhea is particularly severe or you have other concerning symptoms or exposures, it may be appropriate to monitor mild diarrhea for a couple days before seeking Covid-19 testing. Make sure to stay hydrated with fluids like diluted juices, broths, or electrolyte beverages. Avoid dairy, high-fiber foods, sugary drinks, and alcohol which can make diarrhea worse. Over-the-counter anti-diarrheal medications can provide relief but consult your pharmacist or doctor about what may be appropriate for your situation. Maintain good hygiene with frequent handwashing if you have a stomach bug.
Seek prompt medical care if you have signs of dehydration from prolonged diarrhea like excessive thirst, infrequent urination, fast heart rate, lightheadedness, or dark yellow urine. Call your doctor with any concerns or if your diarrhea is not improving within 48 hours. Diarrhea lasting over 2 weeks warrants medical attention. So be aware of your symptoms but do not panic about isolated mild diarrhea – monitor for worsening and stay hydrated.
Conclusions
In summary:
– Diarrhea occurs in only around 7-10% of Covid-19 cases on average based on research studies. Some reports have been higher or lower.
– It appears more common with severe illness requiring hospitalization. But many milder outpatient cases do not have diarrhea.
– Other symptoms like fever and cough are far more common. Diarrhea is likely just a secondary manifestation in some patients.
– Not every infected person experiences the same symptoms. Diarrhea does not definitively occur in all Covid-19 cases.
– Isolated mild diarrhea without other Covid-19 symptoms may not require immediate testing. But worsening diarrhea or multiple symptoms should prompt suspicion.
– Stay hydrated and monitor symptoms if experiencing mild diarrhea. Consult a doctor if it persists beyond 48 hours or with signs of dehydration.
So in conclusion, while diarrhea can certainly occur with Covid-19 and should prompt concern in combination with other symptoms, it is not a consistent defining feature. Diarrhea will not be experienced by every Covid-19 case. But when present alongside more specific symptoms like sudden loss of smell, or with certain risk factors like known viral exposure, diarrhea warrants suspicion of possible Covid-19 and seeking medical assessment.
