Gastrointestinal tract and viral pathogens

Table 1 Common viruses affecting the gastrointestinal system

Virus	Route of infection	Population affected	Type of disease	Diagnosis	Treatment
Norovirus	Fecal-oral, fomites	Children < 5 yr	Gastroenteritis	Self-limited	Supportive
Rotavirus	Fecal-oral, fomites	Children < 5 yr	Gastroenteritis	Self-limited	Supportive
Adenovirus	Fecal-oral, fomites	Any age group, especially children	Gastroenteritis	Self-limited	Supportive
Hepatitis A	Fecal-oral, fomites	Any age groups; international travelers to endemic countries, IV drug users, men who have sex with men	Gastroenteritis, acute viral hepatitis, and fulminant liver failure	Serology	Supportive
Astrovirus	Fecal-oral, fomites	Children < 5 yr	Gastroenteritis	Self-limited	Supportive
Sapovirus	Fecal-oral, fomites	Children < 5 yr	Gastroenteritis	Self-limited	Supportive
Coronavirus	Fecal-oral, fomites	Any age group	Gastroenteritis; respiratory infection	Self-limited, viral rapid antigen, PCR can be performed	Supportive; for COVID-19-antivirals (nirmatrelvir/ritonavir, remdesivir), steroids, biologics (tocilizumab, baricitinib)
Hepatitis E	Fecal-oral, Fomites	15-40 yr	Gastroenteritis, acute hepatitis, and acute liver failure	Serology	Supportive
Cytomegalovirus	Contact with bodily fluids and organ transplantation	All ages	Colitis, toxic megacolon, and peritonitis	Viral PCR	Ganciclovir, valganciclovir, ganciclovir resistant-foscarnet, cidofovir
Herpes simplex virus	Sexual contact	MSM	Proctitis and anal ulcerations	Viral PCR	Acyclovir, valacyclovir, and famciclovir
HIV	Contact through bodily fluids like sexual contact, injection drug use, perinatal transmission	All ages	Acquired immunodeficiency syndrome, HIV enteropathy-diarrhea	2-step testing-combination antigen-antibody test followed by HIV 1/2 differentiation assay	HAART-combination therapy with Tenofovir, Emtricitabine, raltegravir, and bictegravir
Hepatitis B and D	Contact through bodily fluids like sexual contact, injection drug use, perinatal transmission	Usually adults, but all age groups can be affected	Hepatitis, cirrhosis, hepatocellular carcinoma	Serology, DNA load	Acute infections usually resolve; in some cases, tenofovir, entecavir
Hepatitis C	Contact through bodily fluids like sexual contact, injection drug use, transfusion, or perinatal transmission	Usually adults, but all age groups can be affected	Hepatitis, cirrhosis, hepatocellular carcinoma	Serology, RNA load	Combination therapy specific for genotypes; includes sofosbuvir/velpatasvir, glecaprevir/pibrentasvir
Varicella Zoster	Droplet, and contact infection	Commonly in children but can occur in any age group. Reactivation common in immunocompromised	Erosive disease of the stomach and intestines, motility problems	Clinical diagnosis, but RNA PCR is used for atypical presentations	Acyclovir, valacyclovir, and brivudin
Epstein-Barr virus	Contact with bodily fluids, especially saliva; sexual transmission, blood transfusion, organ transplantation	Individuals aged 15-24 yr	Gastritis, Enteritis, esophageal disorders, and gastric cancer	Mostly clinical diagnosis but can be diagnosed by serology	Symptomatic treatment, acyclovir in some cases
HHV-8	Sexual transmission, contact with saliva, blood transfusion, and organ transplantation	All age groups	Maculopapular and polypoid lesions of the GI tract	Endoscopy and biopsy	Radiation, intralesional chemotherapy, or systemic chemotherapy with liposomal doxorubicin and paclitaxel
HPV	Sexual transmission-oral, vaginal, anal sex	15-49 yr	Oropharyngeal, esophageal, gastric, colorectal, and anal cancers	Cytology and viral testing	Cancer-specific treatment

HIV: Human immunodeficiency virus; HPV: Human papillomavirus; HHV: Human herpesvirus 8; MSM: Men who have sex with men; PCR: Polymerase chain reaction; GI: Gastrointestinal.