Can enterovirus colonize the gastrointestinal (GI) system?

Enterovirus as a Colonizer of the Gastrointestinal System

Yes, enteroviruses can colonize the gastrointestinal (GI) tract, serving as their primary site of replication, with individuals capable of shedding the virus in stool for weeks to months after infection. 1

Enterovirus Colonization Characteristics

Enteroviruses primarily infect and multiply in the gastrointestinal tract, which serves as their main entry point into the human body. Key aspects of their GI colonization include:

• Duration of Colonization: Enteroviruses can colonize the throat and gut for weeks to months 1
• Viral Shedding: Peak viral shedding occurs 2-5 days after infection with approximately 100 billion viral copies per gram of feces 1
• Prolonged Excretion:
  • Normal hosts can shed virus in stool for an average of 4 weeks following infection 1
  • Immunocompromised patients can shed enteroviruses in stool for years 1

Clinical Significance of GI Colonization

The presence of enteroviruses in the GI tract has important clinical implications:

• Asymptomatic Carriage: Up to 30% of enterovirus infections are asymptomatic, yet these individuals still shed virus (albeit at lower titers than symptomatic persons) 1
• Interpretation Challenges: Detection of enteroviruses in stool or throat samples must be interpreted cautiously as it may simply reflect colonization rather than active disease 1
• Diagnostic Considerations: Any enterovirus detection in stool samples should be carefully evaluated as it does not automatically imply causation and might simply reflect prolonged excretion 1

Systemic Spread Beyond GI Colonization

While enteroviruses colonize the GI tract, they can spread beyond this site:

• Primary Replication: Initial replication occurs in the gastrointestinal tract and/or upper respiratory tract 2
• Systemic Spread: From the GI tract, enteroviruses can invade the bloodstream and spread to other organs, including the central nervous system 3
• Cell Tropism: Different enterovirus types show varying cell tropism within the intestine:
  • Enteroendocrine cells are permissive to infection
  • Goblet cells appear to resist certain enterovirus infections (e.g., echovirus 11) 4

Public Health Implications

The GI colonization by enteroviruses has significant public health implications:

• Transmission: Enteroviruses spread primarily through fecal-oral and respiratory routes 5
• Water Contamination: Enteroviruses have been identified as indicators of water contamination and are associated with increased risk of gastrointestinal illness in recreational waters 1
• Surveillance: Wastewater surveillance is recommended to monitor enterovirus circulation in communities 2

Common Pitfalls in Interpretation

Several important caveats should be considered when evaluating enterovirus presence in the GI tract:

1. False Attribution: An outbreak or case of gastroenteritis should not be attributed to an enterovirus merely because it was isolated in the stool of an affected person 1
2. Secondary Role in GI Disease: Gastroenteritis plays a minor role in the spectrum of enterovirus disease; their primary disease manifestations often involve other organ systems 1
3. Incidental Finding: Although enteroviruses enter through the gut and may cause incidental mild diarrheal symptoms, their spread to other organs (central nervous system, heart, etc.) produces the major disease manifestations 1
4. Detection vs. Causation: Detection of enterovirus in stool does not necessarily indicate it is the cause of current symptoms 1

In conclusion, enteroviruses are well-established colonizers of the human gastrointestinal tract, using this site for primary replication before potentially causing systemic disease. Their presence in stool samples must be interpreted in the clinical context, as asymptomatic colonization and prolonged shedding are common.