Hepatitis E and Parenteral Transmissionr Aggarwal Brought to You by CORE
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View metadata,Blackwell citation Science, LtdOxford, and UKJGHJournal similar ofpapers Gastroenterology at andcore.ac.uk Hepatology0815-93192004 Blackwell Publishing Asia Pty LtdJuly 2004197729731EditorialHepatitis E and parenteral transmissionR Aggarwal brought to you by CORE provided by Publications of the IAS Fellows Journal of Gastroenterology and Hepatology (2004) 19, 729–731 DOI: 10.1111/j.1400-1746.2004.03454.x EDITORIAL Hepatitis E: Is it a blood-borne pathogen? RAKESH AGGARWAL Department of Gastroenterology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India See article in J. Gastroenterol. Hepatol. 2004; 19: dence of HEV infection was more frequent among those 778–784 who had received blood transfusions than among non- transfused controls. Second, they found that a small Hepatitis E virus (HEV) infection is a common cause of proportion of healthy blood donors had evidence of acute hepatitis in several parts of the world, particularly subclinical HEV infection and viremia. Third, individ- developing countries where there is poor sanitation and uals who had received blood from these donors with environmental conditions.1,2 In these endemic regions, subclinical HEV infection developed evidence of HEV HEV infection accounts for a considerable proportion infection after transfusion. These data suggest (i) fre- of acute sporadic hepatitis. During hepatitis E out- quent existence of subclinical infection and viremia due breaks, the predominant route of transmission of HEV to HEV among healthy persons residing in HEV- has been fecal-oral, in particular through consumption endemic regions, and (ii) the possibility of transmission of contaminated drinking water.3–5 of this virus through blood transfusions. These data Infections that are transmitted by the fecal-oral route, raise several questions. Let us look at these one by one. namely hepatitis A, polio virus and rotavirus infection, Are these data entirely novel? Individual pieces of frequently have a high rate of person-to-person trans- information included in the paper by Khuroo et al.13 mission. However, surprisingly, person-to-person trans- have been reported previously. Mathur et al.,14 using an mission of HEV infection is distinctly uncommon. in-house assay, found IgM anti-HEV antibodies in 244 During outbreaks of hepatitis E, secondary attack rates of 2070 (11.8%) children residing in northern India among household contacts of cases is only 0.7 to and attending medical facilities for minor ailments, sug- 2.2%.1,2 Even when multiple cases occur in a family, gesting that subclinical HEV infection was frequent. these are usually related to a common water source.6 We However, they did not test these sera for HEV RNA. have recently shown person-to-person transmission to Arankalle et al.15 found HEV RNA in sera from three of be uncommon in sporadic hepatitis E also.7 200 blood donors in India; of these three donors, only Ver tical transmission of HEV infection from mother one had detectable IgM anti-HEV antibodies. However, to infant is known. In one study, five of eight babies they did not follow-up the recipients of HEV RNA- born to mothers with acute hepatitis E had HEV RNA positive blood. In another study,16 Arankalle et al. tested in their blood specimens obtained at birth.8 serial sera from 37 IgG anti-HEV-negative transfusion Several hepatotropic viruses, namely hepatitis B virus recipients and found evidence of seroconversion to IgM (HBV), hepatitis C virus (HCV) and hepatitis D virus and IgG anti-HEV in two patients; in contrast, none of (HDV) are transmitted primarily through the parenteral the 34 non-transfused controls showed such serocon- route. In contrast, hepatitis A and E are transmitted pri- version. However, the implicated donor blood units marily by the fecal-oral route. Hepatitis A can rarely be tested negative for HEV RNA, casting a shadow on transmitted through blood transfusion.9 Generally, blood transfusion as the route of transmission. Alterna- HEV is believed not to be transmitted through blood tively, this finding may reflect poor sensitivity of tests for transfusions because viremia during infection with this HEV RNA. The current study by Khuroo et al.,13 in virus lasts for only a short period.10 Also, anti-HEV anti- contrast, provides data concurrently on all pieces of the body prevalence rates among patients with hemo- puzzle. It thus represents a significant advance on the philia,11 thalassemia, patients on hemodialysis and previously available data. intravenous drug users are no higher than those in the Do these data conclusively prove transmission of general population.12 HEV through blood transfusion? Ideally, one would In this issue of the Journal, Khuroo et al.13 provide have liked the authors to show identity or close homol- data to indicate that HEV infection can be transmitted ogy of genomic sequences of HEV isolates from the through blood transfusion. Their study had several infected donor blood and from clinical specimens components. First, they showed that serological evi- obtained from recipients with post-transfusion hepatitis Correspondence: Rakesh Aggarwal, Department of Gastroenterology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow 226014, India. Email: [email protected] Accepted for publication 15 January 2004. 730 R Aggarwal E. Such studies have recently been used to prove trans- another study, only 7% of IgM anti-HEV positive sera mission of HEV through consumption of undercooked from healthy children had ALT levels exceeding twice meat infected with HEV.17 However, even in the the upper limit of normal.14 Thus, ALT elevation is pos- absence of such data, the evidence provided by the sibly too insensitive for this purpose. Furthermore, in a authors is fairly convincing. study from India,18 16.5% of blood units had ALT ele- Do the data reported by Khuroo et al.13 have some vation, indicating that this test would lead to an unac- inconsistency? In the prospective part of their study, ceptably high rate of wastage of donated blood. HEV nearly 4% of healthy blood donors (four of 107, includ- RNA testing is impractical in resource-poor HEV- ing three with IgM anti-HEV) had HEV RNA endemic regions. Further studies are needed on the (Table 1). In contrast, in the initial retrospective study, specificity of IgM anti-HEV assays in blood bank sera only two of 250 (0.8%) healthy controls and none of with a low prevalence of HEV infection. 115 healthy subjects with remote history of transfusion Do the new observations alter our current under- had detectable IgM anti-HEV and/or HEV RNA standing of hepatitis E? Possibly, yes. If confirmed by (Table 1). This significant difference (4/107 vs 2/365; other groups, these findings may have a major impact P < 0.05, Fisher’s exact test; EpiInfo, version 6) in fre- on our understanding of HEV epidemiology. In an quency of subclinical HEV infection rates in the two experimental animal model, subclinical HEV infection phases of their study is somewhat puzzling. Even more has been shown to be associated with excretion in feces disconcerting are a still wider range of IgM anti-HEV of large quantities of viable virus, which is capable of seroprevalence rates reported among healthy subjects in transmitting infection to naïve animals.19 This led to the other studies from India, varying from as low as none of hypothesis that repeated subclinical passage of HEV in 412 blood donors16 to 11.4% of healthy children.14 humans and consequent shedding of large quantities of These variations call for studies of a larger number of viable virus may represent a potential reservoir of HEV, healthy subjects in HEV-endemic populations. somewhat akin to the situation with polio virus. The What is the clinical relevance of transmission of HEV demonstration by Khuroo et al.13 of subclinical HEV infection through blood transfusions? Khuroo et al.13 infection provides support for this hypothesis. found HEV infection in three of their 22 susceptible Khuroo et al.13 found the IgG anti-HEV positivity transfusion recipients; of these three, one each had mild rates to be relatively lower than would be expected from clinical hepatitis, subclinical alanine aminotransferase contemporaneous IgM positivity rates in various study (ALT) elevation and no evidence of liver injury. In the groups (Table 1). After acute HEV infection, IgM anti- study by Arankalle et al.,16 of the two transfusion recip- bodies persist for approximately 5 months. Although ients who developed HEV infection, neither developed the exact duration of persistence of IgG antibodies is symptoms and one had ALT elevation. Thus, based on not known, these are believed to persist for several these limited data on five patients, post-transfusion hep- years.1,2,20 Thus, one would expect the prevalence of IgG atitis E was usually not a clinical problem. Further- to be several fold higher than that of IgM. The relatively more, given the high rates of fecal-oral transmission of low ratio of IgG:IgM positivity rates observed by hepatitis E in disease-endemic regions, the parenterally Khuroo et al. would suggest that IgG antibodies acquired hepatitis E is likely to constitute only a minute become undetectable fairly rapidly. Furthermore, fre- proportion of all hepatitis E cases. quent occurrence of HEV infections, both clinical and Do these data indicate the need to introduce screen- subclinical, among adults in HEV-endemic regions ing measures to prevent transmission of HEV through despite a high rate of subclinical HEV infection suggests blood transfusion? Currently, the answer will be ‘no’. To absence of significant protection against reinfection. If introduce such measures, we need to be certain that this is true, attempts at eradicating hepatitis E through post-transfusion hepatitis E poses a significant disease the development of an immunogenic vaccine may prove burden and that we have a method that reliably prevents to be unsuccessful.