Evidence for widespread infection of wild rats with hepatitis E virus in the United States

Diagnosis and Monitoring of Hepatic Injury. I. Performance Characteristics of Laboratory Tests

Purpose: To review information on performance characteristics for tests that are commonly used to identify acute and chronic hepatic injury.

Data Sources and Study Selection: A MEDLINE search was performed for key words related to hepatic tests, including quality specifications, aminotransferases, alkaline phosphatase, γ-glutamyltransferase, bilirubin, albumin, ammonia, and viral markers. Abstracts were reviewed, and articles discussing performance of laboratory tests were selected for review. Additional articles were selected from the references.

Guideline Preparation and Review: Drafts of the guidelines were posted on the Internet, presented at the AACC Annual Meeting in 1999, and reviewed by experts. Areas requiring further amplification or literature review were identified for further analysis. Specific recommendations were made based on analysis of published data and evaluated for strength of evidence and clinical impact. The drafts were also reviewed by the Practice Guidelines Committee of the American Association for the Study of Liver Diseases and approved by the committee and the Association’s Council.

Recommendations: Although many specific recommendations are made in the guidelines, some summary recommendations are discussed here. Alanine aminotransferase is the most important test for recognition of acute and chronic hepatic injury. Performance goals should aim for total error of <10% at the upper reference limit to meet clinical needs in monitoring patients with chronic hepatic injury. Laboratories should have age-adjusted reference limits for enzymes in children, and gender-adjusted reference limits for aminotransferases, γ-glutamyltransferase, and total bilirubin in adults. The international normalized ratio should not be the sole method for reporting results of prothrombin time in liver disease; additional research is needed to determine the reporting mechanism that best correlates with functional impairment. Harmonization is needed for alanine aminotransferase activity, and improved standardization for hepatitis C viral RNA measurements.

Diagnostic value of immunoglobulin G (IgG) and IgM anti-hepatitis E virus (HEV) tests based on HEV RNA in an area where hepatitis E is not endemic

Acute hepatitis E (AHE) has rarely been reported in industrialized countries, but the rate of seroprevalence of hepatitis E virus (HEV) antibodies (anti-HEV) is inappropriately high. The sensitivity and specificity of the assay used to test for immunoglobulin G (IgG) and IgM anti-HEV have not been well established in areas where hepatitis E is not endemic (hereafter referred to as "nonendemic areas"). We collected serum samples from 13 AHE patients, 271 healthy subjects, and 160 other liver disease patients in Taiwan to test for HEV RNA by reverse transcription (RT)-PCR and for IgG and IgM anti-HEV by enzyme-linked immunosorbent assays. The sensitivities of IgG and IgM anti-HEV (relative to RT-PCR) were 86.7 and 53.3%, respectively. The specificities of IgG and IgM anti-HEV assays for diagnosing AHE were 92.1 and 98.6%, respectively. The rate of seroprevalence of IgG anti-HEV was 11% among healthy subjects in this nonendemic area, and it increased with age. In summary, IgG anti-HEV is a good diagnostic test for screening for AHE in nonendemic areas. The high rate of prevalence of anti-HEV in healthy subjects indicates that subclinical infection may exist.

HEV identified in serum from humans with acute hepatitis and in sewage of animal origin in Spain

BACKGROUND/AIMS

Hepatitis E virus (HEV) is an enterically transmitted pathogen that appears sporadically in non-endemic countries. We studied HEV as a causal agent of acute hepatitis cases in the Spanish population, and the role of pigs as an animal reservoir.

METHODS

The presence of HEV-RNA was analysed by nested polymerase chain reaction in 37 serum samples from patients with acute viral hepatitis, 48 porcine serum samples, 6 pig faecal samples and 12 slaughter-house sewage samples. Presence of antibodies was also tested in porcine sera.

RESULTS

HEV-RNA was found in 3 human serum samples from patients presenting IgG anti-HEV antibodies. Nucleotide sequence analysis identified 2 strains with 93.4% identity, phylogenetically most closely related to the Greece1 isolate, and more closely related to North American and other European strains than to those from endemic regions. HEV-RNA was also detected in slaughterhouse sewage mainly from pigs, presenting 92-94% nucleotide similarity compared to the strains detected in the human sera. Twenty-five per cent of the pigs tested presented IgG anti-HEV antibodies.

CONCLUSIONS

These data suggest that the HEV could be more widespread than previously thought, and present new evidence of the close relationship between HEV strains detected in pigs and those from acute hepatitis patients.

Hepatitis E

Hepatitis E, previously known as enterically transmitted non-A, non-B hepatitis, is an infectious viral disease with clinical and morphologic features of acute hepatitis. Its causative agent, hepatitis E virus, consists of small, 32- to 34-nm diameter, icosahedral, nonenveloped particles with a single-stranded, positive-sense, 7.5-kb RNA. The virus has two main geographically distinct strains, Asian and Mexican; recently, novel isolates from nonendemic areas and a genetically related swine HEV have been described. HEV is responsible for large epidemics of acute hepatitis and a proportion of sporadic hepatitis cases in the Indian subcontinent, southeast and central Asia, the Middle East, parts of Africa, and Mexico. The virus is excreted in feces and is transmitted predominantly by fecal-oral route, usually through contaminated water. Person-to-person transmission is uncommon. Clinical attack rates are the highest among young adults. Recent evidence suggests that humans with subclinical HEV infection and animals may represent reservoirs of HEV; however, further data are needed. Diagnosis of hepatitis E is usually made by detection of specific IgM antibody, which disappears rapidly over a few months; IgG anti-HEV persists for at least a few years. Clinical illness is similar to other forms of acute viral hepatitis except in pregnant women, in whom illness is particularly severe with a high mortality rate. Subclinical and unapparent infections may occur; however, chronic infection is unknown. No specific treatment is yet available. Use of clean drinking water and proper sanitation is currently the most effective method of prevention. Passive immunization has not been proved to be effective, and recombinant vaccines for travelers to disease-endemic areas and for pregnant women currently are being developed.

Risk of hepatitis E infection to travelers

Hepatitis E virus (HEV), previously referred to as enterically transmitted non-A, non-B hepatitis, is a major cause of epidemic hepatitis and acute, sporadic hepatitis in endemic areas of the world. The existence of HEV was suspected based upon epidemiological grounds for many years. However, it was only in the early 1990s that confirmation occurred when two prototype strains of HEV from Burma and Mexico were sequenced.1-3 Outbreaks of HEV infection as well as sporadic transmission commonly occur in Asia, Africa, Central and South America, the Middle East, and the Republics of the former USSR. Southeast Asia seems to be a particularly high HEV endemic region. HEV is transmitted via the fecal-oral route, and contaminated drinking water is a common source of infection.4 Many of the large outbreaks have occurred after heavy rains and flooding.4 During interepidemic periods sporadic infections occur frequently. This suggests a constant environmental reservoir, allowing for transmission between epidemics. The existence of a zoonotic reservoir for the virus is likely. HEV has been detected in a number of species, including swine, rats, and chicken.