Infectious colitis


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M.J. Fernández-Aceñero, M.D., Ph.D.

Last author update: 19 June 2023
Last staff update: 19 June 2023

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PubMed Search: Sapovirus pathology

M.J. Fernández-Aceñero, M.D., Ph.D.
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Cite this page: Fernández-Aceñero MJ. Sapovirus. website. Accessed September 21st, 2023.
Definition / general
  • Acute gastroenteritis is one of the leading causes of death worldwide, mainly in children of developing countries
  • Sapovirus can cause acute gastroenteritis in animals and humans
  • Prevalence can reach 7.5% of pediatric acute gastroenteritis cases
  • No reports on histological features of disease
Essential features
  • Virus belonging to the Caliciviridae family, together with norovirus
  • Emerging cause of acute gastroenteritis, mainly in children, even in developed countries
  • Can sometimes explain both sporadic cases and outbreaks of norovirus negative acute gastroenteritis
  • Formerly called Sapporo-like virus
  • The term typical human caliciviruses was discouraged by the 2002 International Committee on the Taxonomy of Viruses
ICD coding
  • ICD-10: A08.31 - calicivirus enteritis
  • Has a single stranded RNA genome with 2 open reading frames (ORF), coding viral structural proteins (VP1 in the ORF1 and VP2 in the ORF2) (Curr Opin Infect Dis 2020;33:388)
  • 5 genogroups according to the sequence of VP1 and all but GIII can infect humans
  • 19 genotypes: GI, 8 genotypes; GII, 8 genotypes; GIV, 1 genotype; GV, 2 genotypes
  • Sapovirus particles bind to cell surface receptors then enter cells through complex, partially unknown processes and incite pathology (J Virol 2017;91:e00202)
  • Can disrupt epithelial tight junctions through the RhoA-ROCK-MLC signaling pathway and by using occludin as a coreceptor (J Virol 2021;95:e00051, J Virol 2019;93:e01773)
Clinical features
  • Sapovirus was initially discovered in human diarrheic stool samples using electron microscopy in 1976 (Lancet 1976;1:199)
  • No animal model is available, which makes it difficult to obtain antibodies for immune assays (PLoS One 2018;13:e0178157)
  • Despite attempts to grow human sapovirus in cell culture systems, results are not reproducible yet (J Gen Virol 1984;65:1123)
  • Antigen detection methods using ELISA have been developed but lack sensitivity and are not commercially available (Arch Virol 2006;151:551)
  • Real time reverse transcription PCR has become the most widely used method for sapovirus detection (J Clin Virol 2006;35:321)
  • Multiplex studies that can detect several enteral virus are also available (Pathology 2021;53:290)
  • No specific abnormalities
Radiology description
Prognostic factors
Case reports
  • No specific therapy is necessary, other than supportive measures for acute gastroenteritis
  • Usually self limited
  • Some cases require hospital admission (Infect Genet Evol 2005;5:281)
  • In transplanted patients with severe diarrhea due to sapovirus, nitazoxanide has been employed with good outcome (Case Rep Infect Dis 2018;2018:6846873)
Microscopic (histologic) description
  • No report of specific histologic changes in sapovirus infection
  • Biopsy is not indicated
Microscopic (histologic) images

Contributed by M.J. Fernández-Aceñero, M.D., Ph.D.
Slight mucosal changes in sapovirus infection

Slight mucosal changes in sapovirus infection

Electron microscopy description
  • Sapovirus was discovered in diarrheic human stool by electron microscopy
  • Morphology is similar to other caliciviruses
  • Small icosahedral particles (30 - 38 nm) with cup shaped depression on the surface
  • Typical Star of David morphology (Clin Microbiol Rev 2015;28:32)
  • Partially replaced by molecular techniques, although some outbreaks caused by previously unreported genotypes have been resolved with electron microscopy (Euro Surveill 2017;22:30543)
Electron microscopy images

Images hosted on other servers:
Typical morphology of sapovirus Typical morphology of sapovirus

Typical morphology of sapovirus

Molecular / cytogenetics description
  • There are many tools that can help identify the pathogens that lead to acute diarrhea
  • The performance of multiplex PCR testing is better than isolated tests
  • Assays that employ the FilmArrayTM technology can detect 22 of the most frequent gastrointestinal pathogens through rapid PCR multiplexing (BMC Microbiol 2017;17:111)
Sample pathology report
  • Colon, endoscopic biopsy:
    • Active colitis (see comment)
    • Comment: Colonic mucosa with inflammatory expansion of the lamina propria by lymphocytes and plasma cells, associated with slight crypt architectural distortion and few neutrophils. No granulomas or viral inclusions. No dysplasia. The histopathological image is nonspecific and can be associated with drugs, inflammatory bowel disease and bacterial, viral or parasitic infections. Diagnosis should be based on the synthesis of clinical, microbiological and endoscopic data.
Differential diagnosis
  • Inflammatory bowel disease (IBD):
    • Typical clinical and endoscopic features of IBD
    • Biopsy should show continuous crypt distortion, cryptitis and intraluminal microabscesses limited to the mucosa in ulcerative colitis
    • Typical skip lesions, with deep fibrosing ulcers associated or not associated with granulomas or pyloric metaplasia in Crohn's disease
  • Microscopic colitis:
  • Irritable bowel disease, diarrhea associated variant:
    • Largely a diagnosis of exclusion
    • No biopsy is indicated except to rule out other disorders
  • Drug adverse effects:
    • Clinical features are important
    • Apoptosis of epithelial cells and intraepithelial lymphocytes are more prominent (Am J Surg Pathol 2015;39:1653)
  • Other viral causes of diarrhea:
  • Parasites:
    • Can usually be identified in the biopsy samples
  • Bacterial causes of diarrhea:
    • Usually, active colitis with edema and hemorrhage
    • Clinical features and microbiological studies can help diagnosis
Board review style question #1
A 4 year old girl attending a daycare center is brought to hospital by her parents with diarrhea and abdominal pain lasting 2 days, without fever. She was vaccinated against norovirus. Her vital signs are normal. Which of the following is true regarding this patient?

  1. Biopsy is needed to confirm diagnosis
  2. Electron microscopy of a stool sample is mandatory for diagnosis
  3. She must be hospitalized immediately
  4. The symptoms will disappear in a few days with no therapy
Board review style answer #1
D. The symptoms will disappear in a few days with no therapy. Most viral infections disappear spontaneously with no further therapy. Answer A is incorrect because biopsy is not indicated in acute diarrheal diseases. Answer B is incorrect because while it was once the gold standard for diagnosis, electron microscopy has largely been replaced by molecular techniques that are more reliable. Answer C is incorrect because hospitalization need is guided by the clinical situation of the patient. In this case, vital signs were within normal limits.

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Reference: Sapovirus
Board review style question #2
Which of the following techniques is most useful for diagnosis of sapovirus infection?

  1. Biopsy
  2. Complete blood count
  3. Molecular techniques
  4. Serology
Board review style answer #2
C. Molecular techniques. Answers A, B and D are incorrect because in the diagnosis of sapovirus infection, there are no serological assays, no specific analytical abnormalities and no indication for biopsy.

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Reference: Sapovirus
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