The emergence of hepatitis E virus in Europe3 The emergence of hepatitis E virus in Europe reviewfuture science group in the UK, France, Italy, The Netherlands and Germany [64,78,82–85].In

1ISSN 1746-0794Future Virol. (2015) 10(6), 00–00

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10.2217/FVL.15.29 © 2015 Future Medicine Ltd

Review

The emergence of hepatitis E virus in Europe

Ibrahim M Sayed1,2, Koen Vercauteren1, Sayed F Abdelwahab3 & Philip Meuleman*,1

1Center for Vaccinology, Ghent University, Ghent University Hospital, B-9000 Gent, Belgium 2Microbiology & Immunology Department, Faculty of Medicine, Assuit University, Assuit 71515, Egypt 3Microbiology and Immunology Department, Faculty of Medicine, Minia University, Minia 61511, Egypt

*Author for correspondence: Tel.: +32 (0) 9 332 02 05; Fax: +32 (0) 9 332 63 11; [email protected]

AbstrAct Hepatitis E virus (HEV) infections appear to be an emerging problem in Europe. Infections are mainly caused by viruses of genotype 3. Pigs and wild boar are the main reservoirs of HEV in Europe and most autochthonous infections are probably caused by the consumption of uncooked or undercooked infected meat. Nevertheless, transfusion-associated transmission has been described in different European countries but the efficiency of this route of transmission need to be further investigated. Most acute infections are asymptomatic or the induced symptoms are rather nonspecific. Although people that are otherwise completely healthy can spontaneously clear an HEV infection, people with underlying liver disease and/or suffering from immune deficiencies may require treatment to avoid chronicity and exacerbation of liver disease. In this review, we give an epidemiological overview of HEV in Europe and the potential complications.

Keywords • epidemiology • Europe • incidence • prevalence • viral hepatitis

Hepatitis E virus (HEV) causes approximately 20 million infections per year worldwide [1]. HEV is a small non-enveloped virus with icosahedral symmetry, its size is about 27–32 nm and it is classified in the Hepevirus genus of the Hepeviridae family [2]. HEV is subdivided into four major genotypes (gt 1 to 4) that differ in their geographic distribution. HEV of gt 1 and gt 2 infect humans only and are widely distributed in endemic areas as Asia, Africa and Mexico [3,4]. In contrast, HEV isolates of gt 3 and gt 4 are abundant in industrialized developed countries such as European countries, USA and Japan [5–7]. HEV gt 3 and gt 4 have been isolated from humans and a variety of other species such as pigs, wild boar, deer, rabbit, mongoose, cattle and sheep, among others [7–10]. The discovery of new HEV strains isolated from ferret [11], rat [12], chicken [13], bat [14], cutthroat [15], camels [16], moose [17] may require a reclassification of the Hepeviridae family [18,19].

HEV infection was first recognized as an acute self-limiting disease, but these infections can evolve to chronicity in immunocompromised patients such as organ transplant patients and people suffering from HIV infection or hematological disorders [20–22]. The first chronic HEV infections in transplant patients were reported in 2008 by Kamar et al. [23]. In addition, severe complications and death of pregnant women in developing countries, especially in the second and third trimester, were caused by HEV [24,25]. Acute fulminant HEV infections were also reported in Europe [26–29].

Previously HEV was known as epidemic-transmitted non-A, non-B hepatitis virus (NANB) [30]. Balayan et al. reported that oral administration of pooled stool extracts from NANB hepatitis virus led to a clinical manifestation of acute hepatitis [31]. That is why HEV was originally known as enterically transmitted NANB hepatitis virus [31,32]. In 1990, the viral genome was partially cloned and sequenced, and the virus was renamed as HEV [33].

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Historical documents suggest that HEV infections were not uncommon in Europe dur-ing the 17th–19th century [34–36]. From the 20th century, improvements in sanitation and hygiene in Europe and North America led to a decrease in HEV infections in these regions and a confinement to Asia and Africa [32,36].

For long HEV was considered non-endemic in Europe with only sporadic non-epidemic incidents that were mainly associated with travel to endemic areas [37–39]. However, dur-ing the past decade non-travel-associated HEV infections were reported [5,40–43]. In the 1990s, serologic studies among blood donors in Europe and other industrialized countries showed anti-HEV seropositivity of 1.1–1.4%, of which some donors had no history of traveling to hepatitis E endemic regions [39,44–45]. In addition, anti-HEV antibodies (IgG) were documented in pigs (58%), wild boar, rats and other animals in industrialized countries indicating that these animals could represent reservoirs of HEV in these regions [3–4,9,46]. It most be noted that the prevalence of HEV in humans and animals may be underestimated because of the low sensitivity of the first generation antibody tests. The, some-times considerable, differences in seropositivity between different studies conducted in the same county or between different countries may also be explained by the fact that different serologic kits were used.

Hev genotype & subgenotype distributionThe HEV genome consists of a positive sense single stranded RNA of about 7.2-kb long, and includes three open reading frames (ORF) [47]. ORF1 encodes for a nonstructural polypeptide(s) involved in viral replication, with methyl transferase, cysteine protease, helicase and RNA dependent RNA polymerase activi-ties [48]. ORF2 encodes for the viral capsid [49]. ORF3 overlaps with both ORF1 and ORF2 and encodes a phosphoprotein that is involved in virion morphogenesis and egress [50].

As mentioned above, there are at least four genotypes of HEV (gt 1–4) known to cause infection in humans. HEV strains from Europe were shown to be genetically divergent from strains found in the developing countries [7,51].

In Europe HEV gt 3 is responsible for most autochthonous HEV infections [5,42,52]. Gt 3 is further divided into ten (3a–3j) subtypes [7]. In The Netherlands subtypes 3a, 3c and 3f had been isolated from swine [6–7,43,53–54]; while in

Belgium the most common subtype in swine was 3f [6,55]. Subtypes 3c, 3f and 3e are also common in France [7,56]. Recently subtype 3i was iden-tified in kidney transplant recipients in south-eastern France [57]. HEV subtype 3e was also isolated from wild boar in northwestern Italy and Portugal [58,59] and it was recently reported that a virus of this subtype was responsible for the acute fulminant hepatitis case in Roma [26]. HEV of subtype 3e appears to be widely distrib-uted among swine in Finland [60]. In Spain, Gt3f is the most common circulating subtype; it was isolated from human, Spanish swine and sew-age in Barcelona [28,61–62]. In Germany, subtypes 3a, 3b, 3h, 3i and 3j were detected in wild boar samples [63] and subtypes 3a, 3c were found in porcine liver [64]. Both swine and wild boar HEV strains isolated in Germany have high sequence homology with German human HEV strains, supporting a zoonotic source of HEV infec-tions [63,64]. It seems that subtypes 3c, 3e and 3f are the most predominant subtypes in European countries [6–7,43,54–55,58] (Table 1).

HEV gt 4 has 7 subtypes (4a-4g) and is mainly found in Asia where it causes sporadic cases of acute Hepatitis E (AHE) in humans [7]. Several human cases of HEV gt 4 have recently been reported in several European countries such as Germany, France, Italy and Denmark [66,68,70]. In addition, HEV of gt 4 (subtype 4b) has been isolated from swine in Belgium [6]. Gt 4d was isolated from pig farms in the northeast of Italy and was reported as causative agent of an HEV outbreak in Lazio, Italy [65,67]. However, it remains unclear whether gt 4 is more common in Europe or whether these were unique imports from an Asian country [6,68].

Hev transmissionMost HEV infections in Europe are related to zoonotic transmissions. Several animal res-ervoirs have been described for HEV such as swine, rats, wild boars, deer, cows, sheep, goats, camels, horses, rabbit, donkeys, dogs and cats, among others [7–10,71]. In Denmark, novel HEV variants were detected among farmed mink [72]. In Europe, domestic pigs and wild boar are the major reservoirs and source of HEV infec-tions especially for gt 3 viruses [7,41,43,53–54,63,73]. Consumption of undercooked animal products and contact with infected animals are the main risk factors for transmission [42–43,74–82]. The presence of HEV in pork liver sausages, commer-cial porcine liver and porcine ham were reported

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in the UK, France, Italy, The Netherlands and Germany [64,78,82–85]. In Japan, several HEV infection cases associated with ingestion of undercooked deer meat were reported [76]. Although, HEV strains isolated from rabbits in France were genetically close to human HEV, it is not yet confirmed as potential source of infection for humans [86]. Likewise, further investigation is needed to ascertain whether the other animal species mentioned above may pose a potential risk for HEV infection in humans.

Shellfish and other types of marine food represent another risk factor of HEV transmis-sion in Europe and the USA [87–90]. HEV was detected in commercial mussels collected from three different European countries (Greece, Finland and Spain) [89] and also a hepatitis E food-borne outbreak associated with shellfish consumption on a cruise ship was reported [90]. HEV was also reported to be present in environ-mental samples such as waste and surface water in many European countries. For example, in The Netherland HEV was detected in 17% of water samples taken from the Meuse River that runs from France through Belgium into The Netherlands and which is used for recreational purposes and drinking water [43]. In Italy, molec-ular screening of raw sewage from waste water treatment plants revealed that 16% of samples were contaminated with HEV [91]. Also high occurrence of HEV (32%) in wastewater treat-ment plants was observed in Switzerland [92] and in Spain [93]. Contamination of vegetable supply chains with HEV was reported in three different European countries (Greece, Serbia

and Poland) [94]. This represents public health concerns for possibility of transmission of HEV by consumption of raw or minimally processed leafy green vegetables and berry fruits [95]. Both HEV gt 1 and gt 3 were detected in water [43,91–92] which means that both animal and human feces are the source of water contamination. Since almost all autochthonous infections in Europe are of genotype 3, the risk of direct infec-tion through contaminated water must be very limited for European citizens.

A more problematic source of HEV seems to be contaminated blood products. Transmission of HEV by blood transfusion has been reported in several European countries like Great Britain, Germany and France [96–99], but also in Canada and Japan [100–103]. A study in the UK showed that nearly 0.04% of blood donors had HEV RNA in their plasma and that 42% of blood donation recipients developed signs of HEV infection after receiving blood products that contained HEV RNA [99]. HEV transmission after transplantation of the liver from a donor with occult HEV infection was recently reported in Germany [104].

Finally, transplacental and vertical transmis-sion of HEV has been reported in developing countries [25,105–106]. This is usually associ-ated with significant perinatal morbidity and mortality.

Features of disease in patients who acquire HEV infection in developed countries differ from those acquired in developing countries. It has been shown that in Europe the most com-mon group who develops HEV infection are

Table 1. Distribution of hepatitis e virus genotypes and subgenotypes in different european countries.

Genotype Subgenotype and distribution Country Ref.

Gt 3 3a pigs, humans, wild boar, porcine liver

The Netherlands, Germany [7,43,53,63–64]

3b wild boar Germany [63]

3c pigs, pig liver, wild boar, humans The Netherlands, France, Germany

[7,43,53,56,64]

3e pigs, pig liver, water samples, humans, wild boar

The Netherlands, France, Italy, Portugal, Finland

[7,43,56,58–60,65]

3f pigs, pig liver, water samples, humans, wild boar

The Netherlands, France, Spain, Belgium, Italy

[6–7,28,43,56,58,62,65]

3h wild boar, swine Germany, Italy [63,65]

3i wild boar, humans Germany, France [57,63]

3j wild boar Germany [63]

Gt 4 4b humans and pigs Belgium, France [6,66]

4d humans and pigs Italy [65,67] 4f humans Germany [68,69]




Table 2. Seroprevalence of anti-hepatitis e virus antibodies and molecular detection of Hev in different countries in eastern europe.

Country Study group Result Assay used Ref.

Albania Patient with acute viral hepatitis 2.4% of all acute viral hepatitis; 35.7% of acute non-A non-B hepatitis

EIA (Abbott, USA) [110]

Control group (different age) 9.7% (average) Children with thalassemia receiving multiple

transfusionNo positive cases

Pregnant women (at time of delivery) 1.1% (lower than control group) Patients with chronic liver disease (chronic

hepatitis, liver cirrhosis, hepatocellular Carcinomas in cirrhotic patients)

10.5% (no significant difference with control group)

Patients with chronic liver disease 36.6% (positivity increases with age). There is possible association between HEV infection and /or anti-HEV antibodies and advanced stage of chronic liver disease


Control group (people with no apparent liver disease)

12.1%

Croatia Non-A-C acute hepatitis Seropositivity of anti-HEV IgM or IgG was 16.9% by ELISA HEV RNA was detected in some patients.

EIA (Mikrogen, Germany)

[119]

Random HIV infected patients Seropositivity for Anti-HEV IgM and IgG was 1.1%.

Czech Republic (West Bohemia)

Acute hepatitis patients (after elimination of hepatitis A, B, C) Gypsies with nonhepatic disease Venereological patients

27.8% (more in advanced age)

4.8% 2.4%

[112]

Greece Blood donors in the ‘Aretaieion’ Hospital’s Blood Bank, in Athens

Anti-HEV IgG seropositivity was 9.4% ELISA (EIAgen, Adaltis Inc.)

[125]

Hungary Acute non-A-C hepatitis (south west of Hungary)

6.1% had IgG, 1.1% had both IgG and IgM (after confirmation with western blot). All cases were negative by PCR

ELISA (Genelabs Diagnostics Inc.) WB (recomBlot Mikrogen, Germany)

[113]

Acute hepatitis patients (south east of Hungary)

Samples from feces and liver of different animal (pig, wild boar, deer)

9.6% of anti-HEV IgM in human sera (24.5% of these samples were positive by RT PCR and sequencing) 27.3, 34.4 and 12.2% were PCR positive samples from swine (liver, feces), roe-dear (liver) and wild boar (liver) respectively HEV gt3 is endemic in Hungry

ELISA (Dia. Pro Diagnostic Bioprobes, Italy)

[114]

Kosovo Refugees from Kosovo in southern Italy as a result of the 1999 war in the Balkans.

2.5% [115]

Poland Indian students studying in Bialystok Total anti-HEV antibodies were detected in 11.1% of students

[122]

Republic of Moldova

Group 1: swine farmers group 2: person without occupational exposure to swine

51.1% 24.7%

In house ELISA [79]

Romania Control (consecutive subjects asking for a medical examination

No anti-HEV antibodies were detected WB (recomBlot Mikrogen, Germany)

[120]

Very low risk subject (students) Seroprevalence of anti-HEV IgG was 12.5% Low risk subjects (doctors and nurses) Seroprevalence of anti-HEV IgG was 13.98% High risk (hemodialyzed patients) No anti-HEV antibodies were detected Blood donor Seroprevalence of anti-HEV IgG was 14.86% ELISA (MP Biomedicals,

USA)[121]

5



elderly male individuals [5,41,52,107]. This is in clear contrast to developing countries where symptomatic cases have been reported among all age groups and in both sexes, but usually a higher incidence can be observed among males and younger adults [108,109].

Prevalence & emergence of Hev in eastern europeIn eastern European countries, the highest levels of anti-HEV antibodies were found in patients with acute hepatitis or suffering from other liver diseases (Table 2) [110–114]. It was reported that HEV of genotype 3 is endemic in Hungary, where nearly 10% of acute hepatitis cases could be linked to an ongoing or recent HEV infec-tion [114]. However, low prevalence of anti-HEV antibodies (2.5%) was detected in Kosovar refu-gees that arrived in southern Italy during the 1999 Balkan war [115]. In the Republic of Moldova, the level of anti-HEV antibodies was two times higher in swine farmers than in other inhabit-ants [79]. In the Russian Federation, anti-HEV antibodies were reported among blood donors, patients with liver disease, healthcare workers and pregnant women in Kyrgyzstan [116,117]. Recently, higher prevalence of anti-HEV-IgG was detected among Serbian blood donors (15%) [118]. In Croatia, higher prevalence of anti-HEV antibodies was detected among acute non-A-C viral hepatitis patients (16.9%) than among HIV infected patients (1.1%) [119]. In Romania, HEV-specific antibodies were

detected in students, doctors, nurses and blood donors, while no antibodies were detected among hemodialysis patients [120,121]. In Poland, HEV specific antibodies were detected in Indian exchange students, indicating import of HEV from endemic areas to Poland [122]. Recently, anti-HEV antibodies were detected in 44.4% of sera from Polish wild boar, suggesting that these animals might be the main reservoir of HEV in Poland [73]. While low incidence of acute HEV infection was reported in Bulgaria [123], HEV RNA was detected among acute hepatitis patients, pigs and in the surface water samples in Slovenia [124]. The Slovenian strain is a novel iso-late that is distinct from other gt 3 HEV strains isolated in Europe [124]. In Greece, the preva-lence of anti-HEV-IgG among blood donor was 9.4% [125]. Besides an outbreak of HEV infection in Ukraine [126,127], no outbreaks, case-series or case-fatality studies have been reported in many eastern European countries such as Albania, Belarus, Bulgaria, Croatia, Czech Republic, Estonia, Latvia, Republic of Moldova, Romania and Slovakia [127].

Prevalence & emergence of Hev in western europeAlso in western Europe, HEV infection appears to be an emerging problem. Most HEV infection cases reported in the UK were autochthonous. In most cases infections were caused by strains of genotype 3 that closely relate with the virus circulating in British pigs(Table 3)[41–42,128–130].

Country Study group Result Assay used Ref.Russian Federation

Acute viral hepatitis cases in Moscow (All were acquired in central Asia)

2–3.6% [116]

Patients with different liver diseases 5.1–14.3% [117]

Medical workers 5.1% Blood donors with high transaminase levels 5.3% Reference group 1.8%

No seropositivity in healthy pregnant woman in non-endemic area, while 15% seropositivity in pregnant women in endemic area (Kyrgyzstan)

Serbia Blood donors Seropositivity was 15%, increase with age No HEV RNA was detected in seropositive donors

In house ELISA/WB [118]

Slovenia Acute hepatitis E cases during period of 1999–2011

30% of patients had HEV RNA in plasma Molecular assay (PCR) [124]

Stool from Slovenian pigs 20.3% positive for HEV RNA Surface water samples 3.3% positive for HEV RNA

Table 2. Seroprevalence of anti-hepatitis e virus antibodies and molecular detection of Hev in different countries in eastern europe (cont.).




Table 3. Distribution of hepatitis e virus infection in different countries in western europe.

Country Study group Result Assay Ref.

Austria Healthy adults, professional soldiers, and civilians

Overall seropositivity was 14.3%, increased with age Military employment abroad is a risk factor for HEV infection in Austria

ELISA (Fortress Diagnostics Limited, UK)

[141]

Belgium Random patients presenting at the gynecological or orthopedic clinics in Ghent university

Seroprevalence was 14% ELISA (Biorex, UK) [140]

Denmark Danish farmers Prevalence of anti-HEV antibodies was 50.4% In house ELISA [142]

Blood donors in 1983 Prevalence of anti-HEV antibodies was 32.9% Blood donors in 2003 Prevalence of anti-HEV antibodies was 20.6% Finland Case report of acute HEV

infectionDomestic HEV gt3 infection. Elevated liver enzymes and bilirubin. Infection was confirmed by anti-HEV IgM and PCR

[143]

Patient of unexplained hepatitis

Seroprevalence of anti-HEV antibodies was 27.6%. HEV RNA were detected in 8.2%, all of them belong to HEV Gt1


[144]

France Acute hepatitis of unknown etiology

Prevalence of anti-HEV IgG was 10.7%. Most positive samples were confirmed by RT-PCR Circulation of HEV gt3 in south-west France (Midi-Pyrenees)


Acute hepatitis Prevalence of anti-HEV antibodies was low (1%) or less among patients with severe and fulminant acute hepatitis


Blood donors (Ile de France and Pays de Loire)

Seroprevalence of anti-HEV antibodies was 3.2% ELISA (Genelabs Diagnostics Inc.) [146]

Blood donors (Southwestern France)

Anti-HEV antibodies seroprevalence: 52.5%. HEV is endemic in Toulouse

ELISA (Wantai Biologic Pharmacy, China)

[147]

First case report of pregnant woman in South-Eastern France

Acute (gt3f) HEV infection in pregnant woman. Anti-HEV IgM and IgG were detected. Viral clearance was 10 day after acute infection and during 3rd trimester of pregnancy

ELISA (EIAgen; Adaltis Inc., Italy) [148]

Germany Samples reported to Robert Koch Institute

34 cases of acute HEV hepatitis cases. Data indicate sporadically community acquired HEV infection in 5 cases in Germany

EIA (Abbott, USA) WB (recomBlot Mikrogen, Germany)

[149]

Randomly selected surplus samples from diagnostic laboratory in southeastern Germany

Samples from 1996: 50.7% IgG positivity Samples from 2011: 34.3% IgG positivity

ELISA (Wantai Biologic Pharmacy, China) ELISA (Axiom Diagnostics, Germany) WB (recomBlot Mikrogen, Germany)

[150]

First case of acute HEV infection during pregnancy

Acute gt3c HEV infection in pregnant woman. Viral clearance was observed in week 34 of gestation, HEV RNA was below detection limit until the end of pregnancy

EIA (Mikrogen, Germany) WB (recomBlot Mikrogen, Germany)

[151]

Italy Acute non-A-C hepatitis patients

Percentage of anti-HEV antibodies was 6.5%. Only one case was associated with travel to endemic area; the other cases were not.


Percentage of anti-HEV IgG was 56% (78.57% of these samples had anti-HEV IgM) Risk factor: shellfish ingestion Immigration from developing countries may be a cause of circulation of HEV in Catania (eastern Sicily)

EIA (Abbott, USA); in house ELISA”

[152]

Acute HEV was found in 10.1% of patients by detection anti-HEV IgM, seroconversion of HEV-IgG and/or HEV-RNA. New HEV variant native to Italy was identified


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Country Study group Result Assay Ref.Italy (cont.) Cryptogenic acute hepatitis

patients6% of cryptogenic acute hepatitis cases were caused by HEV. Anti-HEV IgM was positive, but PCR results were negative

ELISA (Dia. Pro Diagnostic Bioprobes, Italy)

[153]

General population and healthy controls

Anti-HEV antibodies in healthy controls were 2.6%. Positive correlation between presence of antibodies and age.

In house ELISA [154]

Comparison of seroprevalence of anti-HEV antibodies in 2 groups: general population and pig farmers. Anti-HEV antibodies were 2.9 and 3.3%, respectively Significant difference between anti-HEV-antibodies prevalence in people in Rome (2.5%) and the city of Rieti (5.5%) High prevalence of anti-HEV antibodies among employees of abattoirs

[155]

Anti-HEV antibodies seroprevalence in Lecce was 2.9%

EIA (Abbott, USA) WB (recomBlot Mikrogen, Germany)

[156]

The prevalence of anti-HEV antibodies in general population in the Republic of San Marino was 1.5%. Result confirmed by Western blot

EIA (Abbott, USA) WB (Abbott, Wiesbaden, Germany)

[157]

Prevalence of HEV specific antibodies in Foggia (Apulia, Southern Italy) was 2.7% among Italian general population and 1.3% blood donors

ELISA (Dia. Pro Diagnostic Bioprobes, Italy) WB (Recomblot, Nuclear Laser Medicine, Italy)

[158]

1.3% were positive for anti-HEV IgG and the result were confirmed by western blot Anti-HEV IgM were negative in all samples

ELISA (Dia. Pro Diagnostic Bioprobes, Italy) WB (Recomblot, Nuclear Laser Medicine, Italy)

[159]

Adolescents Anti-HEV antibodies found in 0.4% of young adolescents living in the Molise region in central Italy. HEV could be endemic and not necessarily be imported from endemic area


Portugal Blood donors (Oporto Regional Blood Centre)

Seroprevalence for anti-HEV antibodies was 2.5% (results confirmed by western blot)


Blood donors Chronic liver disease patients

Seroprevalence of anti-HEV antibodies was 4% Seroprevalence of anti-HEV-antibodies was 6.8% Only one case had history of travel to an endemic area.


Sera of Portuguese mothers and their newborn

Anti-HEV IgG seropositivity in mother was 33% and their newborn were also seropositive


[163]

Scotland Blood donors Prevalence of anti-HEV IgG were 4.7%, none positive for anti-HEV IgM


[131]

Acute hepatitis patients Autochthonous HEV gt3 infection was 43%. Some cases had no travel history

ELISA (MD Diagnostics -formerly Genelabs Diagnostics Inc.) WB (recomBlot Mikrogen, Germany)

[132]

Spain Rural area children living in Plasencia (Northern area of Extremadura)

Anti-HEV antibodies prevalence in children was 5.3%. The prevalence in this study was higher than in other European countries.


Urban healthcare people in Valladolid

Anti-HEV antibodies prevalence was found to be 0.8%, which was lower than the prevalence n Spain during the last 20 years


General population of the Community of Madrid

Anti-HEV antibodies positivity: 2.17% ELISA (Dia. Pro, Diagnostic BioProbes, Italy)

[166]

Women in the first trimester of pregnancy

Anti-HEV antibodies prevalence was 3.6%, not significantly higher compared with that in 1990

ELISA (Dia. Pro Diagnostic Bioprobes, Italy) WB (recomBlot Mikrogen, Germany)

[167]

Table 3. Distribution of hepatitis e virus infection in different countries in western europe (cont.).




Country Study group Result Assay Ref. Spain (cont.)

Healthy Children Anti-HEV IgG positivity: 4.6% ELISA (Bioelisa BIOKIT, Barcelona, Spain)

[168]

Patients with elevated serum aminotransferase levels

Detection of anti-HEV IgM in 8.92% of tested subjects (Circulation of autochthonous HEV in Spain)

ELISA (Bioelisa BIOKIT, Barcelona, Spain)

[169]

Blood donors at the Banc de Sang i Teixits (Barcelona)

The prevalence of HEV specific IgG was 19.96% by Wantai assay and 10.72% by Mikrogen assay Three positive cases by Real time PCR

ELISA (Wantai Biologic Pharmacy, China) EIA (Mikrogen, Germany)

[170]

Sweden Healthy volunteers and male pig farmers

Prevalence rate of anti-HEV-IgG in healthy volunteers and male pig farmers was 9.3 and 13%, respectively


Non-A, B, C, D Swedish hepatitis patients, pig fecal samples and wild boar blood samples

HEV RNA were detected in 56.86% of human samples (58/102). Most of these samples were positive anti-HEV IgM 82.78% (48/58), while 17.2% (10/58) were anti-HEV IgG positive. Close relatedness between HEV isolated from human, pig and wild boar samples. HEV is endemic in Sweden

EIA (Abbott, USA) ELISA Diagnostic Biotechnology, Singapore) EIA (Mikrogen, Germany)

[172]

Non-A, B, C, D Swedish and Danish hepatitis patients with a recent travel history

HEV RNA were detected in 71% of patient sera positive for HEV IgM and HEV IgG, while in 18% of patient sera positive for HEV IgG only Autochthonous HEV Gt3 infection in Scandinavia related to pigs reservoir

EIA (Abbott, USA) ELISA Diagnostic Biotechnology, Singapore)

[173]

Switzerland Blood donor in Lausanne, canton of Vaud, southwest Switzerland

Seropositivity of anti-HEV IgG was 4.9%. ELISA (MP Diagnostics -formerly Genelabs Diagnostics Inc.)

[174]

The Netherlands

Blood donors Seroprevalence of anti-HEV antibodies was 1.8% ELISA and WB (Genelabs Diagnostics Inc.)

[135]

Seroprevalence of anti-HEV antibodies was 0.4% EIA (Abbott, USA) ELISA (Genelabs Diagnostics Inc.)

[133]

Seroprevalence of anti-HEV antibodies was 0% (result confirmed by immunoblot)


[134]

Anti-HEV IgG was 27%, of which 3.5% also tested positive for anti-HEV IgM One HEV positive donation per day


[139]

Hepatitis patients (Most of them had history of travel to HEV endemic area)

2.97% positive for anti-HEV antibodies ELISA and WB (Genelabs Diagnostics Inc.)

[135]

3.7% positive for anti-HEV antibodies EIA (Abbott, USA) ELISA (Genelabs Diagnostics Inc.)

[133]

4.4% positive for anti-HEV antibodies (both IgM and IgG), result confirmed by immunoblot - Close relatedness between HEV from patients without travel history and HEV in Dutch pigs


[134]

Report of 3 elderly patients with locally acquired hepatitis E, all were positive anti-HEV IgG by EIA.

ELISA (Genelabs Diagnostics Inc.) EIA (Abbott, USA)

[137]

First group: Non-A-C hepatitis patients, no history of travel to endemic area, no other causes of hepatocellular damage Second group: control group Hepatitis patients : 6.2%, 3.3% level of anti-HEV IgG, anti-HEV IgM, respectively Control: 0.5% level of anti-HEV IgG and anti-HEV IgM

EIA (Abbott, USA) ELISA (Genelabs Diagnostics Inc.)

[138]

Hemophiliac patients Anti-HEV antibodies were 1.4% EIA (Abbott, USA) ELISA (Genelabs Diagnostics Inc.)

[133]


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In Scotland, Cleland and colleagues showed that 4.7% of Scottish blood donors had anti-HEV IgG but not IgM [131]. Ramalingam and col-leagues reported that about 3% of acute hepatitis cases in Scotland were caused by HEV infection, of which more than half were of genotype 3 [132]. Patients with proven HEV infection had traveled to Spain or Turkey, or had not traveled outside Scotland within the incubation period. In The Netherlands, anti-HEV antibody seropositivity was observed in 0.4–1.8% of blood donors [133–135], and between 3 and 6% in patients suf-fering from hepatitis [133–134,136–138]. Locally acquired infections, with no history of travel to an endemic area were also reported in The Netherlands [134,137]. However, a more recent study highlighted higher prevalence rates were in Dutch people that donated blood in the period 2011–2012 (27% anti-HEV IgG positivity) [139]. In Belgium, seroprevalence of anti-HEV IgG in east and west Flanders was 14% [140].

In France, the percentage of anti-HEV anti-bodies in patients suffering from acute hepatitis ranged from 1 to 10.7% [40,145]. About 3.2% of blood donors were seropositive in the ‘Ile de France’ and ‘Pays de Loire’ region [146], while a recent study in southwestern France demon-strated that 52.5% of voluntary blood donors scored anti-HEV IgG positive using a sensitive assay [147]. This high level may be explained by

the possible presence of infectious viral particles in figatellu, a popular dried cold-smoked pork liver sausage [83,175]. In Germany, both travel associated and nontravel associated infections have been reported [149]. Recently, Wenzel and colleagues showed that anti-HEV IgG sero-positivity has declined from 50.7% in 1996 to 34.3% in 2011 in southeastern Germany [150]. In North Germany, seroprevalence of HEV was 6.8% among blood donors [176]. Pischke et al. reported that at least 17% of German popu-lation had been infected with HEV, most infection were acquired within the country rather than imported from tropical areas [177]. Krumbholz and colleagues reported that a very small number of HEV infections occur in children and that seroprevalence increased with age [178]. Recently, two cases of acute HEV infection in pregnant women were reported in France and Germany [148,151]. In Austria, anti-HEV seroprevalence was higher among professional soldiers (20.2%) and individual with previous military employment (21.4%) than in healthy adults and civilians (around 8%) [141]. In Switzerland, a wide variation in HEV seroprevalence (ranging from 4.2 to 21.8%) among the blood donor population was observed [174,179].

In Sweden, 13% of pig farmers tested positive for anti-HEV IgG, which was not significantly

Country Study group Result Assay Ref.United Kingdom

United Kingdom born subjects and non-UK-born subjects (London)

Anti-HEV antibodies level were 3.9% in UK-born subjects and 8.8% in non-UK born subjects. Correlation between presence of immigrants from developing countries and importing HEV infection


Patients with unexplained hepatitis (Southwest England)

6.3% of patients had autochthonous hepatitis E (gt3) that close sequence homology with HEV in UK pigs None of patients had traveled to HEV endemic area; all of them ate pork

ELISA (Genelabs Diagnostics Inc.) [42]

HEV-infected patients (England and Wales)

9% of infections were unrelated to travel to areas where HEV gt3 is endemic. Sequence resembled virus circulating in UK pigs 69% associated with travel to HEV endemic area

ELISA (Genelabs Diagnostics Inc.) [41]

Acute hepatitis patients (Birmingham)

HEV is local acquired in UK. None of HEV infected patients examined had a history of contact with pigs or consumption of undercooked meat Consumption of pork pies or shellfish is a potential source of infection in some cases HEV should be suspected in all cases of acute hepatitis in the UK, regardless of travel history

[129]

General population of all ages Prevalence of anti-HEV IgG was 13% ELISA (Fortress Diagnostics Limited, UK)

[130]


Future Virol. (2015) 10(6)10



higher than the 9.3% found in healthy control individuals [171]. Widen et al. showed that in most IgM-positive samples HEV-RNA could be detected, while HEV RNA was present in only 18–22% of IgG-positive samples [172,173]. In Denmark, high prevalence of HEV specific antibodies was detected among Danish farm-ers (50.4%), this is strongly correlated with zoonotic origin of HEV there [142]. In Finland, a case of acute symptomatic genotype 3 HEV infection was recently reported [143]. Also HEV genotype 1 were detected in Finland among patients of unexplained hepatitis, some of them had history of travel to Asia [144]

In Italy, seroprevalence of anti-HEV anti-bodies was high in non-A non-C hepatitis patients, but low in the general population and in blood donors [37,45,152,154–160]. Intravenous drug users, hemodialysis patients and immi-grants are risk factors for infection in Italy [154–156,158,180]. Likewise, Cacciola et al. reported that 6% of cryptogenic acute hepatitis cases were caused by HEV in Southern Italy [153].

In Spain, inhabitants of rural areas have higher prevalence of anti-HEV antibodies than those in urban areas [164,165]. In the gen-eral population of Madrid 2.17% of tested individuals had anti-HEV antibodies. The fre-quency ranged from 0.97% among the young-est individuals to 3.61% in the oldest [166]. A study in pregnant women living in the same area between 2007 and 2010 showed an overall prevalence rate of 3.6% [167]. A study in chil-dren between 6 and 15 years old living in the northeast of Spain highlighted a seroprevalence of 4.6%, suggesting that some children are already exposed to HEV in their early child-hood [168]. However, higher anti-HEV positiv-ity was detected among patients with elevated aminotransferase plasma levels [169] and pig workers [181]. A recent study on Catalan blood donors has shown that seroprevalence of anti-HEV IgG was about 15% [170]. In Portugal, levels of anti-HEV antibodies among blood donors were between 2.5 and 4% [161,162] and 6.8% among patients with liver diseases [162]. A study on HEV seroprevalence among Portuguese mothers showed that about 33% had anti-HEV IgG, and that their newborns were also seropositive [163]. The latter indi-cating eff icient transplacental transport of HEV-specific IgG.

Importantly, no outbreaks, case series or case fatality studies have been reported in many

western European countries such as Belgium, Denmark, Ireland and Norway [127].

Conclusion & future perspectiveIt is clear that HEV is an emerging problem in Europe, or at least there is an increased aware-ness of the presence of HEV. Most likely, due to lack of routine screening the amount of HEV infections remains underestimated in Europe. In addition, most acutely infected patients only experience nonspecific symptoms so absence of diagnosis and/or misdiagnosis are probably still common. It is noteworthy to mention that seroprevalence rates described in differ-ent studies can considerably be influenced by the assay used. The newest generation screen-ing kits have increased sensitivity which prob-ably also contributes to higher seroprevalence rates [147,170,174,179,182–183].

Recent data show that clearly not all HEV infections in Europe are related to travel to endemic areas, which could be explained by the circulation of HEV in Europe in animal reser-voirs, mainly farmed pigs and wild boar. The exposure to HEV is probably relatively high in Europe most likely as a result of the consump-tion of undercooked infected pork. Since HEV is also circulating in a limited amount of voluntary blood donors, people that require blood trans-fusion are at risk of infection. More studies are required to determine how efficiently the virus present in blood products can be transmitted, and whether the different protocols utilized in blood transfusion centers are adequate enough to minimize or eliminate the risk of viral trans-mission. Alternatively, routine screening for HEV RNA could prevent transfusion-associated transmission.

Especially patients with immune deficiencies (transplant setting, HIV infection, hematologi-cal disorders) are at risk of developing complica-tions during HEV infection in Europe. While most acutely infected people do not require therapy, patients with immune deficiencies will evolve to chronicity and are at risk of develop-ing severe liver disease and cirrhosis [20–22,184–185]. Organ transplant patients can be treated by reducing the immunosuppressive therapy or by administration of ribavirin. However, because of the side effect induced by ribavirin therapy and the identification of viral isolates with decreased sensitivity to ribavirin [186–188] new prophylactic and therapeutic approaches are highly needed [189]. A prophylactic vaccine

11



(Hecolin®) is available in China and it induces 100% protection against HEV infections of genotype 1 and 4 within 1 year after vaccina-tion [190]. Because there is only a single HEV serotype this vaccine probably also induces sterile immunity against viruses of genotype 2 and 3. A 2-year follow-up study indicated that Hecolin vaccination decreased the risk of HEV infection from 2.04% in the control group to 0.3% in the vaccine group [191].Table 3

Financial & competing interests disclosureThe authors have no relevant affiliations or financial involvement with any organization or entity with a finan-cial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pend-ing, or royalties.

No writing assistance was utilized in the production of this manuscript.

executive summAryintroduction

● At least four genotypes of hepatitis E virus (HEV) are known to cause infection in humans.

● Discovery of new HEV strains in a variety of animal species may require reclassification of the Hepeviridae family.

● HEV usually causes acute infections, but chronicity may develop in patients with diminished immunity.

● The incidence of autochtonous HEV infections in Europe is highly underestimated.

Hev genome & genotype distribution

● HEV of genotype 3 is the most frequent cause of HEV infection in Europe. Subtype 3c, 3e and 3f are the most abundant.

Hev transmission

● Pigs and wild boars are probably the main reservoir and source of HEV infection in Europe.

● Transmission of HEV by blood products was documented in some European countries.

Prevalence & emergence of Hev in eastern europe

● High prevalence of HEV-specific antibodies in acute non A–C hepatitis patients.

● HEV seems endemic in several Eastern European countries.

● Anti-HEV antibodies were detected among blood donors.

● In Slovenia a genotype 3 strain circulates that is distinct from the other genotype 3 strains distributed throughout Europe.

Prevalence & emergence of Hev in western europe

● Most HEV infection in Europe are probably autochthonous.

● Recent studies showed higher prevalence of HEV antibodies among blood donors due to the use of more sensitive serologic assays.

● HEV-specific antibodies were detected among the general population indicating endemicity.

● Pig farmers, professional soldiers, intravenous drug users, hemodialysis patients and immigrants are risk factors for HEV infection.

● Cases of pregnant women infected with HEV were reported in France and Germany.

Conclusion

● HEV is an emerging problem in Europe.

● HEV infections are underestimated in Europe due to lack of routine screening and misdiagnosis.

● Screening for HEV RNA may be required to eliminate the risk of HEV transmission during blood donations; especially for patients receiving immunnosuppressive therapy after solid organ transplantation.

● New antiviral therapies are needed for special patient populations.

● A very effective vaccine (Hecolin) is available but it is only licensed in China.

Future Virol. (2015) 10(6)12



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