title: Detailed investigation of ongoing subclinical hepatitis E virus infections; occurring in outbreak settings of North India.
abstract: OBJECTIVE
  Every year globally WHO reports 20 million Hepatitis E virus (HEV) infections. The disease occurs as sporadic cases or focused outbreaks and has potentials to cause massive epidemics. The reservoir of HEV during inter-epidemic period is not well characterized. The sporadic cases usually lack history of contact with clinically overt HEV patients. In the present context we evaluated the occurrence of subclinical HEV as a possible reservoir in endemic region.
  
  
  METHODS
  Blood samples were collected from 67 apparently healthy individuals and 10 acute viral hepatitis (AVH) patients during two HEV outbreaks in North India. The serum samples were tested for anti-HEV IgM, IgG, HEV-IgG avidity index, HEV viral load and conventional-PCR followed by sequencing and phylogenetic analysis.
  
  
  RESULTS
  A total of 14 (20.89%) apparently healthy individuals showed the presence of anti-HEV IgM and IgG. Of 14 based on HEV-IgG avidity index, 9 (64.28%) had secondary-exposure, 4 (28.57%) had primary exposure, while one patient had intermediate avidity. Subclinical subjects with primary exposure had significantly higher anti-HEV IgM index as compared to secondary-exposure (P = 0.0028). Viral load in clinically jaundiced patients was significantly higher as compared to subclinical subjects (P < 0.0001). Phylogenetic analysis showed HEV sequences retrieved from subclinical individuals clustered along with AVH patients, suggesting matched source. The significantly low viral load in subclinical subjects hints towards the dose dependency for progression of clinical manifestation.
  
  
  CONCLUSIONS
  We document subclinical HEV with low level viremia occurs during outbreak settings and goes un-noticed, which helps maintaining the virus in nature possibly leading to its endemicity.
authors.affiliation: Department of Virology, Postgraduate Institute of Medical Education & Research, Chandigarh, 160012, India.
authors.forename: Manasi
authors.initials: M
authors.lastname: Majumdar
authors.forename: Mini P
authors.initials: MP
authors.lastname: Singh
authors.forename: Kapil
authors.initials: K
authors.lastname: Goyal
authors.forename: Yogesh
authors.initials: Y
authors.lastname: Chawla
authors.forename: Radha K
authors.initials: RK
authors.lastname: Ratho
mesh_terms: D000293:Adolescent; D000328:Adult; D004196:Disease Outbreaks; D005260:Female; D006508:Hepatitis Antibodies / Q000097:blood*; D016751:Hepatitis E / Q000175:diagnosis / Q000453:epidemiology*; D016752:Hepatitis E virus / Q000235:genetics / Q000302:isolation & purification*; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007075:Immunoglobulin M / Q000097:blood*; D007194:India / Q000453:epidemiology; D008297:Male; D010802:Phylogeny; D012367:RNA, Viral / Q000097:blood*; D012698:Serologic Tests; D019562:Viral Load; D055815:Young Adult
chemical_list: D006508:Hepatitis Antibodies; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D012367:RNA, Viral
keywords: avidity ELISA; hepatitis E virus; phylogenetic analysis; subclinical infections; viral load