The relationship between adenovirus infections and irritable bowel syndrome (IBS) remains an area of ongoing investigation. IBS is a chronic functional gastrointestinal (GI) disorder with multifactorial origins, and while viral infections have been implicated in the development or exacerbation of certain diseases, including IBS, their specific role is not yet fully understood. While some research has explored the potential link between viral infections and the onset or worsening of IBS symptoms, including studies on norovirus and cytomegalovirus, evidence specifically focusing on adenoviruses is limited.

Overview

IBS Is a chronic functional GI disorder characterized by symptoms such as abdominal pain, bloating, and changes in bowel habits.¹ It affects from 10 to 15% worldwide.² The exact cause of IBS is not fully understood, various factors, including changes in gut motility, visceral hypersensitivity, intestinal inflammation, and alterations in the gut microbiota may be involved. Of note, about 10% of patients develop IBS after an intestinal infection.³

Adenoviruses are a group of viruses that can cause a range of illnesses, including respiratory infections, conjunctivitis, and gastroenteritis.⁴

The association between viruses and some diseases determined by multifactorial causes, including IBS, suggests that viral infections may interact with genetic, environmental, and immunological factors to initiate or exacerbate disease processes. However, it's important to note that the exact mechanisms by which viruses may contribute to these conditions are still being investigated.

Given evidence that some individuals with IBS report a history of viral gastroenteritis, the question arises: is there a correlation between adenovirus infection and IBS? 

This article aims to explore this question by reviewing existing research, examining potential mechanisms of interaction, discussing clinical implications, and highlighting opportunities for future research. 

Adenovirus infections: insights and impacts

Overview of adenoviruses

Adenoviruses represent a cluster of DNA viruses capable of infecting humans and inducing various illnesses. Typical manifestations of adenovirus infection encompass respiratory symptoms such as cough, sore throat, and fever. Additionally, GI symptoms including diarrhoea, vomiting, and abdominal pain are frequently reported. Although pervasive across all age groups, adenoviruses are prevalent among children.⁵

Adenoviruses can enter the body through various routes, including respiratory droplets, fecal-oral transmission, and direct contact with contaminated surfaces, consequently, they often proliferate in enclosed or densely populated environments.

Upon entering the GI tract, adenoviruses can infect the epithelial cells lining the intestines, leading to inflammation and disruption of normal gut function, leading to symptoms typical of gastroenteritis.

Understanding adenovirus-associated gastroenteritis

Acute adenovirus gastroenteritis typically presents with a sudden onset of symptoms, including diarrhoea, vomiting, fever, and abdominal cramps. Fortunately, most cases of acute adenovirus gastroenteritis are self-limiting and resolve within a few days to a week with supportive care such as hydration and rest. However, especially in individuals with compromised immune systems or underlying medical conditions, adenovirus gastroenteritis can progress to a chronic infection. Chronic adenovirus gastroenteritis may exhibit prolonged or recurrent GI symptoms, often necessitating medical intervention.⁶

IBS

Definition, diagnosis and symptoms

IBS is a chronic functional GI disorder characterized by recurrent abdominal pain or discomfort associated with changes in bowel habits, such as diarrhoea, constipation, or both. Diagnosis of IBS is typically based on the Rome criteria.Of note, IBS is a diagnosis of exclusion, meaning other GI conditions must be ruled out before a diagnosis of IBS can be made. Common symptoms of IBS include abdominal pain or discomfort, bloating, gas, and changes in bowel habits. However, they can vary in severity and frequency, leading to significant disruption of daily activities, work, and social life.

The unpredictable nature of IBS symptoms can also cause emotional distress, anxiety, and depression, further impacting the overall quality of life for individuals with the condition.

Current understanding of IBS pathophysiology

The exact cause of IBS is not fully understood, but it is believed to involve multiple factors, including alterations in gut motility, visceral hypersensitivity, intestinal inflammation, and alterations in the gut microbiota.

Dysregulation of the brain-gut axis, which involves communication between the brain and the gut, may also play a role in the development and exacerbation of IBS symptoms.⁷

Recent research has also implicated immune system dysfunction, genetic predisposition, and psychosocial factors in the pathogenesis of IBS, highlighting the complex nature of the condition.⁸

Unveiling the association between viral infections and IBS

Researchers have investigated the potential link between viral infections and certain diseases that have unknown causes and are considered to have multifactorial origins, such as multiple sclerosis (MS), lupus, rheumatoid arthritis (RA)and inflammatory bowel disease (IBD). It has been reported that viral infections are considered one of the possible causes or triggers for these conditions.⁹

This does not mean that viruses are the sole cause of these diseases, but rather that they may contribute to their development in certain individuals or under specific circumstances.

Viral infections and IBS: examining existing research

Researchers explored the potential link between viral infections and the development or exacerbation of IBS symptoms. These studies have primarily focused on common viral pathogens such as norovirus, rotavirus, and enterovirus, examining their prevalence and impact on GI symptoms in individuals with IBS. 

For instance, the study of Zanini et al. showed that a significant portion of patients who had norovirus developed IBS within a year following the initial infection.¹⁰

In the research conducted by Marshall et al., they highlighted the significant role of noroviruses in triggering IBS symptoms following episodes of acute viral gastroenteritis induced by foodborne pathogens.¹¹

Another study aimed to determine the prevalence of Cytomegalovirus in IBD patients displayed that 10% of patients had Cytomegalovirus infection. While Cytomegalovirus infection may indicate disease severity in IBD patients, it does not appear to affect morbidity or mortality.¹²

A recent review highlighted that individuals who have previously been exposed to SARS-CoV-2 experienced persistent gastrointestinal symptoms and an increased likelihood of developing functional GI disorders, suggesting a potential correlation between prior infection with the virus and the onset of GI issues.¹³

These studies, while not specifically focusing on adenoviruses, offer valuable insights into the broader association between viral infections and the manifestation of IBS symptoms.

Mechanisms of interactions

Viral infections can trigger GI symptoms through:

• direct damage to the intestinal epithelium, leading to inflammation and disruption of normal gut function¹⁴
• alterations in intestinal permeability, affecting the absorption of nutrients and water and leading to symptoms such as diarrhoea, abdominal pain, and bloating¹⁵
• stimulation of the release of pro-inflammatory cytokines and chemokines, possibly induced by viral replication within the GI tract.¹⁶
• Immune system-mediation: persistent or chronic viral infections may elicit prolonged immune activation and inflammation within the GI tract. 

Dysregulated immune responses can contribute to the development of chronic GI conditions, through mechanisms such as immune cell infiltration, tissue damage, and alterations in gut barrier function.¹⁷ Immune-mediated pathways involved in the response to viral infections may overlap with those implicated in the pathogenesis of chronic GI conditions, suggesting potential links between viral infections and the development of IBS.

Research gap: adenovirus in IBS cases

While adenoviruses are known to infect the GI tract and cause symptoms such as diarrhoea and abdominal pain, their role in the development or exacerbation of IBS symptoms remains unclear.

So far, only one study has investigated the relationship between adenoviruses and IBS. Zangouey et al. compared adenovirus frequency in IBS patients and healthy individuals. The results revealed that adenovirus DNA was detected in the majority of both IBS patients and controls, with no significant difference in viral loads between the two groups.¹⁸ Hence, the study suggests that adenovirus infection is not likely to play a significant role in the development of IBS. 

Limitations of existing research

Overall, existing research on the association between viral infections, including adenovirus, and IBS is inconclusive and has several limitations.

To mention, many studies rely on self-reported symptoms or retrospective data, which may introduce bias and limit the reliability of findings.

Additionally, the heterogeneity of study populations, viral strains, and methodologies makes it challenging to draw definitive conclusions.

Future research utilizing prospective study designs, standardized diagnostic criteria, and molecular techniques to detect viral pathogens may help clarify the relationship between viral infections and IBS.

Furthermore, investigating potential interactions between adenovirus infection, host immune responses, and alterations in the gut microbiota could provide valuable insights into the pathogenesis of IBS and inform targeted therapeutic interventions.

Clinical implications and future directions

Patients presenting with GI symptoms suggestive of viral infection should be assessed for the possibility of underlying IBS, particularly if symptoms persist or recur beyond the acute phase of infection.

Continued research is essential to better understand the potential correlation between adenovirus infection and the development or exacerbation of IBS symptoms. Prospective studies utilizing molecular techniques to detect adenovirus and longitudinal follow-up of patients with viral gastroenteritis may help establish temporal relationships and identify potential risk factors for the development of IBS.

Summary

• While adenovirus infection can cause GI symptoms such as diarrhoea and abdominal pain, the relationship between adenovirus infection and IBS remains unclear
• Existing research on the association between viral infections, including adenovirus, and IBS is inconclusive and limited by methodological challenges
• Potential mechanisms of interaction between adenovirus infection and IBS include immune-mediated pathways and alterations in gut homeostasis, but further research is needed to elucidate these mechanisms