Epidemiology and Global Burden

Hepatitis E virus (HEV), a non-enveloped, positive-sense, single-stranded RNA virus belonging to the Hepeviridae family (genus Orthohepevirus, species HEV-A), is a globally significant cause of acute viral hepatitis. According to the WHO, HEV causes an estimated 20 million infections annually, resulting in 3.3 million symptomatic cases and over 44,000 deaths—primarily due to acute liver failure (ALF) in pregnant women and chronic infection in immunocompromised individuals.

• Endemic regions:HEV genotype 1 (G1) and G2 predominate in resource-limited settings of Asia (e.g., India, Pakistan, Bangladesh), North and West Africa, where large waterborne outbreaks occur following monsoons or infrastructure failures.
• Zoonotic transmission (autochthonous cases): Genotypes 3 and 4 are enzootic in Europe, North America, Japan, and Australia, with transmission via consumption of undercooked meat (especially pork, wild boar, and deer) or contact with infected animals. In Europe, zoonotic HEV accounts for >90% of reported cases.
• Other routes: Blood transfusion (documented in the UK, France, and the US), vertical transmission (mother-to-child), and organ transplantation (donor-derived infection) are increasingly recognized.

Pathophysiology and Clinical Manifestations

HEV enters via the oropharynx, replicates in the intestinal epithelium, spreads to the liver via viremia, and causes hepatocellular injury through both direct cytopathic effects and host immune responses (CD4+/CD8+ T-cell–mediated inflammation).

Acute Infection in Immunocompetent Hosts

• Incubation period: 15–60 days (median ~28 days); symptoms typically emerge 2–8 weeks post-exposure.
• Clinical features (present in 20–30% of cases, more frequent and severe in adults >25 years):
  • Prodrome: Fever, malaise, anorexia, nausea/vomiting
  • Hepatic signs: Right upper quadrant pain, jaundice, dark urine, pale stools
  • Extrahepatic manifestations (emerging evidence): Neurological (Guillain-Barré syndrome, Bell’s palsy), renal (acute interstitial nephritis), hematologic (thrombocytopenia), and pancreatic involvement.

Note: Most immunocompetent adults recover spontaneously within 2–6 weeks. Fulminant hepatic failure occurs in 0.5–4% of cases, with highest risk in:

• Pregnant women (particularly third trimester; mortality up to 20–30% with G1)
• Patients with pre-existing chronic liver disease (e.g., HBV, HCV, alcohol-related cirrhosis)

Special Populations at High Risk for Severe Disease

Diagnostic Evaluation: Modern Algorithm with Laboratory Guidance

Indications for Testing

Per AASLD (2023) and EASL (2024) guidelines, test for HEV in:

• Any patient with unexplained acute hepatitis (ALT/AST >100 U/L + bilirubin elevation)
• Immunocompromised individuals with elevated LFTs (even if asymptomatic)
• Pregnant women with severe hepatitis or ALF
• Patients with extrahepatic manifestations suggestive of HEV

Laboratory Testing Strategy

First-line: Serology + RT-PCR (combined approach)

Note: EU/US FDA-cleared assays are limited; many labs use in-house or CE-marked tests with genotype-dependent performance. WHO International Standard (IS 97/628) enables standardization.

Clinical Management: Evidence-Based Recommendations

1. Immunocompetent Patients

• Management: Supportive care only (no antivirals indicated).
• Avoid hepatotoxins: Alcohol, acetaminophen >2 g/day (ideally ≤2 g in severe cases).
• Pregnancy-specific considerations:
  • Monitor maternal oxygenation, coagulation (INR), and mental status for ALF
  • Transfer to tertiary center with liver transplant capability if signs of fulminant hepatitis
  • No evidence supports antiviral use in acute pregnancy HEV—ribavirin is teratogenic (Category C)

2. Immunocompromised Patients (e.g., SOT recipients)

Per AASLD 2023 and EASL 2024 guidelines:

• First-line: Ribavirin monotherapy
  • Dose: 600–800 mg/day (weight-based; max 1,200 mg/day), adjusted for renal function (CrCl <50 mL/min → reduce dose)
  • Duration: Minimum 12 weeks; continue until HEV RNA undetectable x12 weeks post-treatment
  • Efficacy: Sustained virologic response (SVR) rates of 80–90% in treated patients vs. <10% with spontaneous clearance in chronic cases
  • Monitoring: HEV RNA q2–4 weeks; CBC (ribavirin-induced hemolytic anemia in ~30%—check Hgb baseline & monthly)
• Second-line options if ribavirin fails/contraindicated:
  • Reduce immunosuppression (e.g., taper calcineurin inhibitors to target troughs: tacrolimus <5 ng/mL, cyclosporine <100 ng/mL) — effective in ~40–60% when combined with ribavirin
  • Pegylated interferon-α (IFN-α): Reserved for non-kidney transplant recipients due to risk of graft rejection; contraindicated in decompensated cirrhosis
  • Direct-acting antivirals (DAAs): Sofosbuvir ± ribavirin shows promise in case reports (virologic success ~70%), but no RCTs; not recommended as first-line

3. Chronic HEV & Liver Transplant Recipients

• Untreated chronic HEV can progress to fibrosis/cirrhosis within 2–5 years
• Monitor annually with HEV RNA if immunosuppressed (e.g., pre-transplant screening in endemic areas)
• If graft HEV+ post-transplant: Treat even if asymptomatic (viral load >10⁴ IU/mL)

Emerging Issues & Clinical Pearls

• Extrahepatic manifestations: HEV is linked to neural disorders (e.g., GBS—OR 7.5 in meta-analysis) and acute kidney injury. Consider HEV PCR in unexplained neurological syndromes with recent hepatitis.
• Vaccine availability: Hecolin® (recombinant ORF2 protein, genotype 4) is licensed in China, India, and Nepal; efficacy >90% over 4.5 years. Not WHO-prequalified or FDA-approved—availability limited.
• Blood safety: Nucleic acid testing (NAT) for HEV implemented in UK (2017), Netherlands, and France; reduces transfusion transmission from ~1:2,000 to <1:100,000 units. US FDA recommends donor screening but does not mandate NAT.
• Differential diagnosis:
  • Acute hepatitis: Exclude HAV, HBV, HCV, HDV, drug-induced liver injury (e.g., acetaminophen, antibiotics), autoimmune hepatitis (ANA/ASMA positive)
  • Chronic hepatitis with elevated LFTs in immunocompromised: Test HEV RNA before escalating immunosuppression

Conclusion

HEV is no longer a “tropical disease” but a global health concern due to zoonotic transmission and iatrogenic spread. Prompt diagnosis—using combined serology and RT-PCR—is critical, especially in high-risk groups. In immunocompromised patients, ribavirin-based therapy guided by viral load monitoring significantly improves outcomes. Clinicians should maintain high suspicion for HEV in any patient with unexplained hepatitis, regardless of travel history.

References (Latest Guidelines & Evidence)

1. World Health Organization. Hepatitis E. Fact Sheet, Updated May 2024.
2. Kamar N et al. Hepatitis E Virus Infection. N Engl J Med. 2023;389(5):447–458.
3. European Association for the Study of the Liver (EASL). Clinical Practice Guidelines on Hepatitis E Virus. J Hepatol. 2024;80(2):256–274.
4. AASLD. AASLD Practice Guidance on Hepatitis E. Hepatology. Published online March 2023.
5. Saini RK et al. Ribavirin for Chronic Hepatitis E: Systematic Review and Meta-Analysis. Liver Int. 2024;44(1):78–89.
6. van der Poort R et al. HEV Infection in Solid Organ Transplant Recipients: Outcomes and Management. Clin Infect Dis. 2023;77(Suppl 3):S245–S253.