The unique riverine ecology of hepatitis E virus transmission in South-East Asia

Hepatitis E Virus Research in Brazil: Looking Back and Forwards

Hepatitis E virus (HEV) has emerged as a public health concern in Brazil. From the first identification and characterization of porcine and human HEV-3 strains in the 2000s, new HEV subtypes have been identified from animal, human, and environmental isolates. As new potential animal reservoirs have emerged, there is a need to compile evidence on the zoonotic dissemination of the virus in animal hosts and the environment. The increasing amount of seroprevalence data on sampled and randomly selected populations must be systematically retrieved, interpreted, and considered under the One Health concept. This review focused on HEV seroprevalence data in distinct animal reservoirs and human populations reported in the last two decades. Furthermore, the expertise with experimental infection models using non-human primates may provide new insights into HEV pathogenesis, prevention, and environmental surveillance.

Hepatitis E Virus: An emerging enigmatic and underestimated pathogen

Hepatitis E virus (HEV) is an RNA virus causing hepatitis E disease. The virus is of one serotype but has diverse genotypes infecting both humans and animals. Based on evidence from seroprevalence studies, about 2 billion people are estimated to have been infected with HEV globally. HEV, therefore, poses a significant public health and economic challenge worldwide. HEV was discovered in the 1980s and was traced back to the 1955 - 1956 outbreak of hepatitis that occurred in India. Subsequently, several HEV epidemics involving thousands of individuals have occurred nearly annually in different countries in Asia and Africa. Initially, the virus was thought to be only enterically transmitted, and endemic in developing countries. Due to the environmental hygiene and sanitation challenges in those parts of the world. However, recent studies have suggested otherwise with the report of autochthonous cases in industrialised countries with no history of travel to the so-called endemic countries. Thus, suggesting that HEV has a global distribution with endemicity in both developing and industrialised nations. Studies have also revealed that HEV has multiple risk factors, and modes of transmission as well as zoonotic potentials. Additionally, recent findings have shown that HEV leads to severe disease, particularly among pregnant women. In contrast to the previous narration of a strictly mild and self-limiting infection. Studies have likewise demonstrated chronic HEV infection among immunocompromised persons. Consequent to these recent discoveries, this pathogen is considered a re - emerging virus, particularly in the developed nations. However, despite the growing public health challenges of this pathogen, the burden is still underestimated. The underestimation is often attributed to poor awareness among clinicians and a lack of routine checks for the disease in the hospitals. Thus, leading to misdiagnosis and underdiagnosis. Hence, this review provides a concise overview of epidemiology, diagnosis, and prevention of hepatitis E.

Viral hepatitis: Milestones, unresolved issues, and future goals

In this review the current overall knowledge on hepatitis A, B, C, D, and E will be discussed. These diseases are all characterized by liver inflammation but have significant differences in distribution, transmission routes, and outcomes. Hepatitis B virus and hepatitis C virus are transmitted by exposure to infected blood, and in addition to acute infection, they can cause chronic hepatitis, which in turn can evolve into cirrhosis. It is estimated that more than 300 million people suffer from chronic hepatitis B or C worldwide. Hepatitis D virus, which is also transmitted by blood, only affects hepatitis B virus infected people, and this dual infection results in worse liver-related outcomes. Hepatitis A and E spread via the fecal-oral route, which corresponds mainly to the ingestion of food or water contaminated with infected stools. However, in developed countries hepatitis E is predominantly a zoonosis. Although hepatitis A virus and hepatitis E virus are usually responsible for a self-limiting hepatitis, a serious, rarely fatal illness is also possible, and in immunosuppressed patients, such as organ transplant recipients, hepatitis E virus infection can become chronic. The description of goals achieved, unresolved issues, and the latest research on this topic may make it possible to speculate on future scenarios in the world of viral hepatitis.

Laundry Hygiene and Odor Control: State of the Science

Laundering of textiles—clothing, linens, and cleaning cloths—functionally removes dirt and bodily fluids, which prevents the transmission of and reexposure to pathogens as well as providing odor control. Thus, proper laundering is key to controlling microbes that cause illness and produce odors. The practice of laundering varies from region to region and is influenced by culture and resources. This review aims to define laundering as a series of steps that influence the exposure of the person processing the laundry to pathogens, with respect to the removal and control of pathogens and odor-causing bacteria, while taking into consideration the types of textiles. Defining laundering in this manner will help better educate the consumer and highlight areas where more research is needed and how to maximize products and resources. The control of microorganisms during laundering involves mechanical (agitation and soaking), chemical (detergent and bleach), and physical (detergent and temperature) processes. Temperature plays the most important role in terms of pathogen control, requiring temperatures exceeding 40°C to 60°C for proper inactivation, while detergents play a role in reducing the microbial load of laundering through the release of microbes attached to fabrics and the inactivation of microbes sensitive to detergents (e.g., enveloped viruses). The use of additives (enzymes) and bleach (chlorine and activated oxygen) becomes essential in washes with temperatures below 20°C, especially for certain enteric viruses and bacteria. A structured approach is needed that identifies all the steps in the laundering process and attempts to identify each step relative to its importance to infection risk and odor production.

Hepatitis E in Sub Saharan Africa - A significant emerging disease

Hepatitis E is an emerging endemic disease found across the African continent, but there are clear differences in epidemiology between North Africa and countries south of the Sahara. In this systematic review, Google scholar and PubMed databases were searched for peer-reviewed articles on HEV epidemiology. Publications meeting our inclusion criteria were critically reviewed to extract consistent findings and identify knowledge gaps. Hepatitis E has been reported in 25 of the 49 countries in Sub Saharan Africa.

Mortality rates of 1–2% in the general population and ~ 20% in pregnant women. Outbreaks were closely linked to refugees and Internally Displaced Persons in camps which accounted for 50% of reported outbreaks. There was very little research and concrete evidence for sources of contamination and transmission routes. There are indications of zoonotic transmission of Hepatitis E Virus infection but further research in these fields is required.

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No data from 50% of African countries

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Outbreaks closely linked to refugee and IDP camps

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Little data on sources of HEV contamination

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Indications but little evidence of zoonotic transmission

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Low awareness amongst health professionals and general public

Seroprevalence of Dromedary Camel HEV in Domestic and Imported Camels from Saudi Arabia

Hepatitis E Virus (HEV) imposes a major health concern in areas with very poor sanitation in Africa and Asia. The pathogen is transmitted mainly through ingesting contaminated water or food, coming into contact with affected people, and blood transfusions. Very few reports including old reports are available on the prevalence of HEV in Saudi Arabia in humans and no reports exist on HEV prevalence in camels. Dromedary camel trade and farming are increasing in Saudi Arabia with importation occurring unidirectionally from Africa to Saudi Arabia. DcHEV transmission to humans has been reported in one case from the United Arab Emeritus (UAE). This instigated us to perform this investigation of the seroprevalence of HEV in imported and domestic camels in Saudi Arabia. Serum samples were collected from imported and domestic camels. DcHEV-Abs were detected in collected sera using ELISA. The prevalence of DcHEV in the collected samples was 23.1% with slightly lower prevalence in imported camels than domestic camels (22.4% vs. 25.4%, p value = 0.3). Gender was significantly associated with the prevalence of HEV in the collected camels (p value = 0.015) where males (31.6%) were more infected than females (13.4%). This study is the first study to investigate the prevalence of HEV in dromedary camels from Saudi Arabia. The high seroprevalence of DcHEV in dromedaries might indicate their role as a zoonotic reservoir for viral infection to humans. Future HEV seroprevalence studies in humans are needed to investigate the role of DcHEV in the Saudi human population.

Population density and water balance influence the global occurrence of hepatitis E epidemics

In developing countries, the waterborne transmission of hepatitis E virus (HEV), caused by HEV genotypes 1 (HEV-1) and 2 (HEV-2), leads to the onset of large recurrent outbreaks. HEV infections are of particular concern among pregnant women, due to very high mortality rates (up to 70%). Unfortunately, good understanding of the factors that trigger the occurrence of HEV epidemics is currently lacking; therefore, anticipating the onset of an outbreak is yet not possible. In order to map the geographical regions at higher risk of HEV epidemics and the conditions most favorable for the transmission of the virus, we compiled a dataset of HEV waterborne outbreaks and used it to obtain models of geographical suitability for HEV across the planet. The main three variables that best predict the geographical distribution of HEV outbreaks at global scale are population density, annual potential evapotranspiration and precipitation seasonality. At a regional scale, the temporal occurrence of HEV outbreaks in the Ganges watershed is negatively correlated with the discharge of the river (r = -0.77). Combined, our findings suggest that ultimately, population density and water balance are main parameters influencing the occurrence of HEV-1 and HEV-2 outbreaks. This study expands the current understanding of the combination of factors shaping the biogeography and seasonality of waterborne viral pathogens such as HEV-1 and HEV-2, and contributes to developing novel concepts for the prediction and control of human waterborne viruses in the near future.

Effects of Boiling Drinking Water on Diarrhea and Pathogen-Specific Infections in Low- and Middle-Income Countries: A Systematic Review and Meta-Analysis

Globally, approximately 2 billion people lack microbiologically safe drinking water. Boiling is the most prevalent household water treatment method, yet evidence of its health impact is limited. To conduct this systematic review, we searched four online databases with no limitations on language or publication date. Studies were eligible if health outcomes were measured for participants who reported consuming boiled and untreated water. We used reported and calculated odds ratios (ORs) and random-effects meta-analysis to estimate pathogen-specific and pooled effects by organism group and nonspecific diarrhea. Heterogeneity and publication bias were assessed using I2, meta-regression, and funnel plots; study quality was also assessed. Of the 1,998 records identified, 27 met inclusion criteria and reported extractable data. We found evidence of a significant protective effect of boiling for Vibrio cholerae infections (OR = 0.31, 95% confidence interval [CI] = 0.13-0.79, N = 4 studies), Blastocystis (OR = 0.35, 95% CI = 0.17-0.69, N = 3), protozoal infections overall (pooled OR = 0.61, 95% CI = 0.43-0.86, N = 11), viral infections overall (pooled OR = 0.83, 95% CI = 0.7-0.98, N = 4), and nonspecific diarrheal outcomes (OR = 0.58, 95% CI = 0.45-0.77, N = 7). We found no evidence of a protective effect for helminthic infections. Although our study was limited by the use of self-reported boiling and non-experimental designs, the evidence suggests that boiling provides measureable health benefits for pathogens whose transmission routes are primarily water based. Consequently, we believe a randomized controlled trial of boiling adherence and health outcomes is needed.

Seroprevalence and incidence of hepatitis E virus among blood donors: A review

Hepatitis E virus (HEV) is an RNA virus with 4 main genotypes. HEV-1 and HEV-2 infect solely humans, while HEV-3 and HEV-4 infect humans and various animals such as pigs, deer, and rabbits. HEV-5 and HEV-6 infect mainly wild boar. Recently, new genotypes, known as HEV-7 and HEV-8, were found to infect camels and humans. HEV is globally distributed into different epidemiological patterns based on socioeconomic factors and ecology. Although HEV is mainly transmitted through the fecal-oral route, it was also recognized as a transfusion-transmitted virus. Transmission through blood donation was documented worldwide with rising annual observations, accounting for more than 2.5% of all transmissions. HEV infection is usually asymptomatic or subclinical in immunocompetent individuals, so it remains questionable whether there is an urgent need to screen for HEV prior to blood transfusion. Moreover, recent studies conducted in the Middle East and North Africa (MENA) region indicate that HEV is highly endemic. Here, we provide a review on HEV epidemiology, transmission, and laboratory diagnosis, giving special emphasis to the newly discovered genotypes, HEV-7 and HEV-8. Furthermore, we underscore the findings of recent HEV seroprevalence and viremia studies among blood donors worldwide. We also shed light on similar studies performed among blood donors in the MENA region.

Seroprevalence and risk factors of hepatitis E virus infection among the Korean, Manchu, Mongol, and Han ethnic groups in Eastern and Northeastern China

Hepatitis E virus (HEV) infection is a serious public health concern in developing countries. China is regarded as an HEV-endemic area, but epidemiological data for HEV among different nationalities is limited. This study was conducted to estimate the seroprevalence and risk factors of HEV infection in Koreans (n = 520), Manchus (n = 303), Mongols (n = 217), and Hans (n = 802) in Eastern and Northeastern China between 2013 and 2015. A total of 366 (19.87%) out of 1842 samples were seropositive for IgG or IgM HEV-antibodies detected by enzyme-linked immunoassays. Among these groups, the Mongols had the highest seroprevalence of HEV infection (25.35%, 55/217), followed by the Koreans (23.65%, 123/520), the Manchus (19.80%, 60/303), and the Hans (15.96%, 128/802). Multiple analysis showed that the gender, consumption of raw/undercooked meat, source of drinking water, residence area, and age were significantly associated with HEV infection in four ethnic groups. The present results indicated that HEV infection was prevalent in Mongols, Koreans, Manchus, and Hans in the surveyed regions, which demonstrated the higher risk of transmitting HEV in multiple nationalities in Eastern and Northeastern China.

Production and characterization of a Brazilian candidate antigen for Hepatitis E Virus genotype 3 diagnosis

Hepatitis E, caused by hepatitis E virus (HEV), is a viral infectious pathology of great importance in the public health. Hepatitis E outbreaks were registered in developing countries with poor or no sanitation, where drinking water was contaminated with fecal material, but also in many industrialized countries probably due to consumption of HEV-positive swine meat. In this study, we present the development and characterization of a recombinant antigen from ORF2 HEV genotype 3. Viral RNA was extracted from swine feces infected with the native virus. A total of 267 residues from the C-terminal ORF2((394-661)) coding sequence were cloned into the pET20a vector and expressed in Escherichia coli ER2566. Recombinant protein was purified by liquid chromatography and the fragment obtained a 98% homology against other human or swine HEV genotype 3 ORF2 sequences. Wistar rats were inoculated with ORF2p, developing antibodies able to recognize both the homologous antigen and the native HEV genotype 3 ORF2 present in infected stool. In parallel, HEV-negative swine were experimentally challenged with HEV genotype 3. ORF2 was detected by PCR 14 days post-inoculation in three-fourth piglets' feces and one week later by dot blot. In conclusion, this study proved the immunogenic and antigenic properties of the recombinant protein ORF2p.

Hepatitis E virus infection: Epidemiology and treatment implications

Hepatitis E virus (HEV) infection is now established as an emerging enteric viral hepatitis. Standard treatments in acute and chronic hepatitis E remain to be established. This study undertakes a review of the epidemiology, treatment implication and vaccine prevention from published literature. HEV infection is a worldwide public health problem and can cause acute and chronic hepatitis E. HEV genotypes 1 and 2 are primarily found in developing countries due to waterborne transmission, while the zoonotic potential of genotypes 3 and 4 affects mostly industrialized countries. An awareness of HEV transmission through blood donation, especially in the immunocompromised and solid organ transplant patients, merits an effective anti-viral therapy. There are currently no clear indications for the treatment of acute hepatitis E. Despite concerns for side effects, ribavirin monotherapy or in combination with pegylated interferon alpha for at least 3 mo appeared to show significant efficacy in the treatment of chronic hepatitis E. However, there are no available treatment options for specific patient population groups, such as women who are pregnant. Vaccination and screening of HEV in blood donors are currently a global priority in managing infection. New strategies for the treatment and control of hepatitis E are required for both acute and chronic infections, such as prophylactic use of medications, controlling large outbreaks, and finding acceptable antiviral therapy for pregnant women and other patient groups for whom the current options of treatment are not viable.

Prevalence of Endemic Pig-Associated Zoonoses in Southeast Asia: A Review of Findings from the Lao People's Democratic Republic

The increasing intensification of pork production in southeast Asia necessitates an urgent requirement to better understand the dual impact of pig-associated zoonotic disease on both pig production and human health in the region. Sharing porous borders with five countries and representing many regional ethnicities and agricultural practices, the Lao People's Democratic Republic (Lao PDR) appears well placed to gauge the levels of pig-associated zoonoses circulating in the wider region. Despite this, little is known about the true impact of zoonotic pathogens such as leptospirosis, Trichinella, hepatitis E virus (HEV), Japanese encephalitis (JE), and Taenia solium on human health and livestock production in the country. A comprehensive review of the published prevalences of these five pig-associated zoonoses in Lao PDR has demonstrated that although suspicion remains high of their existence in pig reservoirs across the country, epidemiological data are scarce; only 31 epidemiological studies have been undertaken on these diseases in the past 25 years. A greater understanding of the zoonoses prevalence and subsequent risks associated with pork production in the southeast Asian region could help focus public health and food safety interventions at key points along the value chain, benefiting both livestock producers and the broader animal and human health systems in the region.

Cultural drivers and health-seeking behaviours that impact on the transmission of pig-associated zoonoses in Lao People's Democratic Republic

Pig rearing is an important income source in the Lao People's Democratic Republic (PDR), with many smallholder farmers using traditional free-range pig production systems. Despite the potentially significant health risks posed by pig production regarding pig-associated zoonoses, information on the sociocultural drivers of these zoonoses is significantly lacking. This review summarises the existing sociocultural knowledge on eight pig-associated zoonoses suspected to be endemic in Southeast Asia: brucellosis, Q fever (Coxiella burnetii), trichinellosis, hepatitis E virus, leptospirosis, Japanese encephalitis, Streptococcus suis and Taenia solium taeniasis-cysticercosis. It summarises current knowledge on these diseases grouped according to their clinical manifestations in humans to highlight the propensity for underreporting. A literature search was conducted across multiple databases for publications from 1990 to the present day related to the eight pig-associated zoonoses and the risk and impact connected with them, with Lao PDR as a case study. Many of these pig-associated zoonoses have similar presentations and are often diagnosed as clinical syndromes. Misdiagnosis and underreporting are, therefore, substantial and emphasise the need for more robust diagnostics and appropriate surveillance systems. While some reports exist in other countries in the region, information is significantly lacking in Lao PDR with existing information coming mainly from the capital, Vientiane. The disease burden imposed by these zoonoses is not only characterised by morbidity and mortality, but directly impacts on livelihoods through income reduction and production losses, and indirectly through treatment costs and lost work opportunities. Other factors crucial to understanding and controlling these diseases are the influence of ethnicity and culture on food-consumption practices, pig rearing and slaughter practices, hygiene and sanitation, health-seeking behaviours and, therefore, risk factors for disease transmission. Published information on the knowledge, attitudes and beliefs of people regarding pig zoonoses and their risk factors is also extremely limited in Lao PDR and the broader Southeast Asian region. The need for more transdisciplinary research, using a One Health approach, in order to understand the underlining social determinants of health and their impacts on health-seeking behaviours, disease transmission and, ultimately, disease reporting, cannot be more emphasized.

Hepatitis E virus: foodborne, waterborne and zoonotic transmission

Hepatitis E virus (HEV) is responsible for epidemics and endemics of acute hepatitis in humans, mainly through waterborne, foodborne, and zoonotic transmission routes. HEV is a single-stranded, positive-sense RNA virus classified in the family Hepeviridae and encompasses four known Genotypes (1–4), at least two new putative genotypes of mammalian HEV, and one floating genus of avian HEV. Genotypes 1 and 2 HEVs only affect humans, while Genotypes 3 and 4 are zoonotic and responsible for sporadic and autochthonous infections in both humans and several other animal species worldwide. HEV has an ever-expanding host range and has been identified in numerous animal species. Swine serve as a reservoir species for HEV transmission to humans; however, it is likely that other animal species may also act as reservoirs. HEV poses an important public health concern with cases of the disease definitively linked to handling of infected pigs, consumption of raw and undercooked animal meats, and animal manure contamination of drinking or irrigation water. Infectious HEV has been identified in numerous sources of concern including animal feces, sewage water, inadequately-treated water, contaminated shellfish and produce, as well as animal meats. Many aspects of HEV pathogenesis, replication, and immunological responses remain unknown, as HEV is an extremely understudied but important human pathogen. This article reviews the current understanding of HEV transmission routes with emphasis on food and environmental sources and the prevalence of HEV in animal species with zoonotic potential in humans.

Hepatitis e: epidemiology and natural history

Hepatitis E is a disease caused by infection with hepatitis E virus (HEV). The virus has four genotypes, named 1 to 4, with one shared serotype. Genotypes 1 and 2 infect only humans, whereas genotypes 3 and 4 primarily infect several mammalian animals, with occasional transmission to humans. Evidence of infection with HEV has been found in most parts of the world, with two distinct epidemiological patterns. In areas with high disease endemicity, primarily developing countries in Asia and Africa, the disease occurs as outbreaks and as sporadic cases of acute hepatitis, and is caused exclusively by infection with genotypes 1 or 2 HEV, which is acquired through fecal-oral route, usually through contamination of water supplies. The disease in these areas occurs most commonly in young adults, and is particularly severe in pregnant women and persons with pre-existing chronic liver disease; chronic infection has not been reported. In areas with lower endemicity, which are mainly developed areas with robust water supply and sanitation systems, occasional sporadic cases of locally-acquired genotype 3 or 4 HEV infection are observed. The affected persons are often elderly and have other coexisting illnesses. The reservoir of infection in these areas is believed to be in animals, such as pigs, wild boar and deer, with zoonotic transmission to humans, possibly through consumption of undercooked meat. Also, in these areas, persistent HEV infection has been well documented among immunosuppressed persons such as organ transplant recipients, and is believed to lead to chronic liver injury, including liver cirrhosis. Further work is needed to better understand the biological basis underlying these widely-differing epidemiological patterns.

An exploratory case control study of risk factors for hepatitis E in rural Bangladesh

Hepatitis E virus (HEV) is the major cause of epidemic and sporadic hepatitis globally. Outbreaks are associated with fecal contamination of drinking water, yet the environmental reservoir of HEV between epidemics remains unclear. In contrast to neighboring countries, where epidemics and sporadic disease co-occur, HEV-endemic communities in rural Bangladesh seldom report outbreaks; sporadic hepatitis E is reported from urban and rural areas of the country. Besides typical enteric risk factors, other routes for HEV infection and disease are unclear. We conducted monthly household surveillance of a southern Bangladeshi community of 23,500 people to find incident cases of acute hepatitis E over a 22 month period. An algorithm was used to capture 279 candidate cases, of which 46 were confirmed acute HEV infections. An exploratory case-control study was conducted to identify putative risk factors for disease. Nearly 70% of cases were over 15 years old. Female gender seemed protective (OR:0.34) against hepatitis E in this conservative setting, as was the use of sanitary latrines (OR:0.28). Socioeconomic status or animal exposures were not significant predictors of disease, although outdoor employment and recent urban travel were. Unexpectedly, recent contact with a “jaundiced” patient and a history of injection exposure in the 3 months prior to disease (OR:15.50) were significant. Susceptible individuals from “endemic” communities share similar enteric exposure risks to those commonly associated with tourists from non-endemic countries. This study also raises the novel possibility of parenteral and person-to-person transmission of HEV in non-epidemic, sporadic disease settings.

Increased risk of hepatitis E virus infection in schizophrenia

Until now, the risk of HEV infection in schizophrenia was unknown. The present results showed that the seroprevalence of anti-HEV IgG and anti-HEV IgM in schizophrenia were significantly higher than that in healthy controls. Anti-HEV IgG positivity increased with age and with the duration of disease in schizophrenia patients. Moreover, schizophrenia patients with increased CD4⁺/CD8⁺ T-cell ratios (>2.03) had higher anti-HEV IgG detection rates than those with normal ratios (1.05-2.03). Compared with the schizophrenia patients who tested anti-HEV IgG negative, the levels of interleukin-4 and interleukin-10 (Th2 cytokines) were significantly higher, while the interleukin-12 (Th1 cytokine) level was significantly lower, in those with anti-HEV IgG positivity. Of five schizophrenia patients who were anti-HEV IgM positive, four had elevated CD4⁺/CD8⁺ T-cell ratios. HEV RNA was isolated from one of these four patients and classified as genotype 4. Anti-HEV IgM positivity was not detected among healthy controls. Therefore, schizophrenia patients exhibited a higher risk of HEV infection than controls.

Serologic study of pig-associated viral zoonoses in Laos

We conducted a serologic survey of four high-priority pig-associated viral zoonoses, Japanese encephalitis virus (JEV), hepatitis E virus (HEV), Nipah virus (NiV), and swine influenza virus (SIV), in Laos. We collected blood from pigs at slaughter during May 2008–January 2009 in four northern provinces. Japanese encephalitis virus hemagglutination inhibition seroprevalence was 74.7% (95% confidence interval [CI] = 71.5–77.9%), JEV IgM seroprevalence was 2.3% (95% CI = 1.2–3.2%), and HEV seroprevalence was 21.1% (95% CI = 18.1–24.0%). Antibodies to SIV were detected in 1.8% (95% CI = 0.8–2.8%) of pigs by screening enzyme-linked immunosorbent assay, and only subtype H3N2 was detected by hemagglutination inhibition in two animals with an inconclusive enzyme-linked immunosorbent assay result. No NiV antibody–positive pigs were detected. Our evidence indicates that peak JEV and HEV transmission coincides with the start of the monsoonal wet season and poses the greatest risk for human infection.

Hepatitis E

Hepatitis E refers to liver disease caused by the hepatitis E virus (HEV), a small, nonenveloped virus with a single-stranded RNA genome. The virus has four genotypes, but only one serotype. Genotypes 1 and 2 exclusively infect humans, whereas genotypes 3 and 4 also infect pigs and several other mammalian species. Though HEV does not grow well in cell culture, several aspects of its biology and pathogenesis have been worked out using animal models and cell transfection studies, and by analogy with other related viruses. HEV itself appears noncytopathic, and the liver injury during hepatitis E may be mediated by the host immune response. In areas with poor sanitation, HEV infection is common and presents as outbreaks and also as sporadic cases with acute self-limited hepatitis. The transmission is feco-oral, usually through contaminated drinking water. The disease often affects young adults and is particularly severe among pregnant women and persons with preexisting liver cirrhosis. In the developed world, the disease is being increasingly recognized. It occurs as occasional sporadic cases, most often among elderly men with coexisting illnesses. These appear to be related to zoonotic transmission. Chronic infection is known among immunosuppressed persons in these regions and may progress to liver cirrhosis. Serological tests for diagnosis of HEV exposure and recent infection, namely immunoglobulin (Ig)G and IgM anti-HEV, respectively, need further improvement in sensitivity and specificity, particularly when used in developed countries. Two recombinant protein vaccines have undergone successful human trials, but are not yet commercially available. Recent development of cell-culture methods for HEV should allow a better understanding of this enigmatic agent.

Hepatitis E virus is prevalent in the pig population of Lao People's Democratic Republic and evidence exists for homogeneity with Chinese Genotype 4 human isolates

The objective of this study was to determine the prevalence and genotypic range of Hepatitis E virus (HEV) in the pig population of northern Lao People's Democratic Republic (PDR). We collected 181 faecal samples from indigenous-breed pigs ≤ 6 months of age and the faeces was stored in RNA stabilisation buffer due to cold-chain and transport limitations. Twenty-one (11.6%) pigs had detectable HEV RNA and 43.5% of village pig herds were infected. Based on a 240 base pair-nucleotide sequence flanking the junction of open reading frames 1, 2 and 3 (ORF1, ORF2 and ORF3) the isolates were phylogenetically classified within genotype 4. Phylogenetic analyses revealed distinct genetic groupings of the Lao HEV isolates and two groups clustered with human and pig HEV isolates from China. This was the first study to demonstrate genotype 4 HEV in Lao PDR and indicates pigs are a potential reservoir for human HEV infection.

From barnyard to food table: the omnipresence of hepatitis E virus and risk for zoonotic infection and food safety

Hepatitis E virus (HEV) is an important but extremely understudied pathogen. The mechanisms of HEV replication and pathogenesis are poorly understood, and a vaccine against HEV is not yet available. HEV is classified in the family Hepeviridae consisting of at least four recognized major genotypes. Genotypes 1 and 2 HEV are restricted to humans and associated with epidemics in developing countries, whereas genotypes 3 and 4 HEV are zoonotic and responsible for sporadic cases worldwide. The identification and characterization of a number of animal strains of HEV from pigs, chickens, rabbits, rats, mongoose, deer, and possibly cattle and sheep have significantly broadened the host range and diversity of HEV. The demonstrated ability of cross-species infection by some animal strains of HEV raises public health concerns for zoonotic HEV infection. Pigs are a recognized reservoir for HEV, and pig handlers are at increased risk of zoonotic HEV infection. Sporadic cases of hepatitis E have been definitively linked to the consumption of raw or undercooked animal meats such as pig livers, sausages, and deer meats. In addition, since large amounts of viruses excreted in feces, animal manure land application and runoffs can contaminate irrigation and drinking water with concomitant contamination of produce or shellfish. HEV RNA of swine origin has been detected in swine manure, sewage water and oysters, and consumption of contaminated shellfish has also been implicated in sporadic cases of hepatitis E. Therefore, the animal strains of HEV pose not only a zoonotic risk but also food and environmental safety concerns.

Hepatitis E: Historical, contemporary and future perspectives

Hepatitis E was suspected for the first time in 1980 during a waterborne epidemic of acute hepatitis in Kashmir, India. In the 30 years since then, a small virus with single-stranded RNA genome has been identified as the cause of this disease and named as hepatitis E virus (HEV). The virus has four genotypes; of these, genotypes 1 and 2 are known to infect only humans, whereas genotypes 3 and 4 primarily infect other mammals, particularly pigs, but occasionally cause human disease. In highly-endemic areas, the disease occurs in epidemic and sporadic forms, caused mainly by infection with genotype 1 or 2 virus, acquired through the fecal-oral route, usually through contaminated water supplies. The disease is characterized by particularly severe course and high mortality among pregnant women. In persons with pre-existing chronic liver disease, HEV superinfection can present as acute-on-chronic liver disease. In low-endemic regions, sporadic cases of locally-acquired HEV infection are reported; these are caused mainly by genotype 3 or 4 HEV acquired possibly through zoonotic transmission from pigs, wild boars or deer. In these areas, chronic infection with genotype 3 HEV, which may progress to liver cirrhosis, has been reported among immunosuppressed persons. Two subunit vaccines containing recombinant truncated capsid proteins of HEV have been shown to be highly effective in preventing the disease; however, these are not yet commercially available. These vaccines should be of particular use in groups that are at high risk of HEV infection and/or of poor outcome.

Epidemiology of hepatitis E: current status

Hepatitis E, caused by infection with hepatitis E virus (HEV), is a common cause of acute hepatitis in areas with poor sanitation. The virus has four genotypes with one serotype: genotypes 1 and 2 exclusively infect humans, whereas genotypes 3 and 4 also infect other animals, particularly pigs. In endemic areas, both large outbreaks of acute hepatitis as well as sporadic cases occur frequently. These cases are usually due to genotype 1 or 2 HEV and are predominantly caused by fecal-oral transmission, usually through contamination of drinking water; contaminated food, materno-fetal (vertical spread) and parenteral routes are less common modes of infection. The acute hepatitis caused by this virus has the highest attack rates in young adults and the disease is particularly severe among pregnant women. HEV superinfection can occur among persons with pre-existing chronic liver disease. In non-endemic regions, locally acquired disease was believed to be extremely uncommon. However, in recent years, an increasing number of cases, due mostly due to genotype 3 or 4 HEV, have been recognized. These are more often elderly men who have other coexisting illnesses, and appear to be related to zoonotic transmission from pigs, wild boars and deer, either food-borne or otherwise. Also, chronic infection with genotype 3 HEV has been reported among immunosuppressed persons in these regions. A subunit vaccine has been shown to be effective in preventing clinical disease, but is not yet commercially available. Our understanding of hepatitis E epidemiology has undergone major changes in recent years, and the future may hold even more surprises.

Hepatitis E: a complex and global disease

Thirty years after its discovery, the hepatitis E virus (HEV) continues to represent a major public health problem in developing countries. In developed countries, it has emerged as a significant cause of non-travel-associated acute hepatitis. HEV infects a wide range of mammalian species and a key reservoir worldwide appears to be swine. Genomic sequence similarity between some human HEV genotypes and swine HEV strains has been identified and we know that humans can acquire HEV infection from animals. Although for the most part the clinical course of HEV infection is asymptomatic or mild, significant risk of serious disease exists in pregnant women and those with chronic liver disease. In addition, there are data on the threat of chronic infections in immunocompromised patients. Beyond management of exposure by public health measures, recent data support that active immunisation can prevent hepatitis E, highlighting the need for vaccination programmes. Here we review the current knowledge on HEV, its epidemiology, and the management and prevention of human disease.

Identification of genotype 4 hepatitis E virus strains from a patient with acute hepatitis E and farm pigs in Bali, Indonesia

A previous study revealed that antibodies to hepatitis E virus (HEV) (anti-HEV) are highly prevalent among healthy individuals and farm pigs in Bali, Indonesia, and suggested that HEV infection may occur via zoonosis among Balinese people. However, there were no reports of acute hepatitis E in Bali. To elucidate whether Balinese HEV strains recovered from infected humans and pigs have significant sequence similarity, serum samples obtained from 57 patients (age, mean +/- standard deviation, 31.1 +/- 11.9 years) with sporadic acute hepatitis and from one hundred and one 2- or 3-month-old farm pigs in Bali were tested for anti-HEV and HEV RNA. Among the 57 patients, 2 (3.5%) had high-titer IgM/IgA class anti-HEV antibodies and one of them had detectable HEV RNA (BaliE03-46). Overall, 58 pigs (57.4%) tested positive for anti-HEV, while 5 pigs (5.0%) had detectable HEV RNA. Based on the 412-nucleotide sequence within open reading frame 2, the BaliE03-46 isolate and the 5 swine HEV isolates recovered from the viremic pigs were phylogenetically classified in genotype 4, but were only 77.3-90.8% identical to the genotype 4 HEV isolates reported thus far in China, India, Japan, Taiwan, and Vietnam. The BaliE03-46 isolate of human origin shared high identities of 97.3-98.3% with 4 of the 5 Balinese swine isolates, but differed by 16.1% from the remaining swine isolate. These results suggest that indigenous HEV strains of genotype 4 with marked heterogeneity are circulating in Bali, Indonesia, and that pigs are reservoirs of HEV for Balinese people who have a habit of ingesting uncooked pigs.

Evaluation of diagnostic assays for hepatitis E virus in outbreak settings

Hepatitis E virus (HEV) is a major cause of hepatitis. We evaluated five HEV antibody diagnostic assays by using outbreak specimens. The Abbott immunoglobulin G (IgG), Genelabs IgG, and Walter Reed Army Institute of Research (WRAIR) IgM assays were about 90% sensitive; the Abbott IgG and WRAIR total Ig and IgM assays were more than 90% specific.

Identification of genotype 1 hepatitis E virus in samples from swine in Cambodia

Hepatitis E virus (HEV) is a major enterically transmitted pathogen in many developing countries, where it causes outbreaks and sporadic cases of acute hepatitis. A study conducted with pigs from several livestock farms in Cambodia identified one swine genotype 1 HEV isolate as being associated with prevalent swine genotype 3 HEV.

UK acquired hepatitis E--An emerging problem?

Eight cases of hepatitis E acquired in the UK are reported. These cases presented to an inner city hospital in Birmingham, UK, over a 5-month period in 2005. HEV is considered unusual in the UK and generally occurs after travel to endemic regions. Only five cases of hepatitis E acquired in the UK have been reported in the literature. This series represents an increase in the local incidence of hepatitis E, particularly that of UK-acquired infection. HEV should be considered in all patients with acute hepatitis, irrespective of travel history.

Infectious swine hepatitis E virus is present in pig manure storage facilities on United States farms, but evidence of water contamination is lacking

Fresh feces, manure slurry (from earthen lagoons and/or concrete pits), and drinking and surface water samples were collected from 28 pig farms in the Midwestern United States. All samples were tested for hepatitis E virus (HEV) RNA by reverse transcription-PCR. Seven of 28 farms had fecal samples that contained HEV. Of 22 farms where pit samples were accessible, 15 contained HEV, and of 8 farms that had lagoons, 3 contained HEV. The highest virus titers were 10 and 10(3) genome equivalents per 60 ml of manure slurry in lagoon and pit samples, respectively. None of the water samples tested HEV positive. To determine the infectivity of the HEV found in the positive farm 19 lagoon (designated L19) or farm 12 pit (designated P12) samples, pigs were inoculated either intravenously (n = 3) or orally (n = 3) with the L19 or P12 manure slurry. Four pigs inoculated intravenously with prototype swine HEV served as positive controls. All positive-control pigs shed HEV in feces and 3 of 4 developed anti-HEV antibodies. Two pigs in the intravenously inoculated P12 group shed HEV in feces, and one of the pigs seroconverted to anti-HEV antibodies. None of the pigs in the negative-control, L19 oral, L19 intravenous, or P12 oral group shed HEV in feces. The findings indicate that HEV found in pig manure slurry was infectious when inoculated intravenously. Pit manure slurry is a potential source of HEV infection and for contamination of the environment. Contamination of drinking or surface water with HEV was not found on or near the pig farms.

Prevalence of antibodies to hepatitis E virus among apparently healthy humans and pigs in Bali, Indonesia: Identification of a pig infected with a genotype 4 hepatitis E virus

In Indonesia where hepatitis E virus (HEV) is believed to be highly endemic, only three outbreaks of HEV transmission have been documented to date in restricted areas (West Kalimantan and East Java). A total of 1,115 serum samples collected from apparently healthy individuals in Bali, Lombok, and Surabaya in Indonesia in 1996 where epidemic HEV transmissions have never been reported, were tested for IgG class antibodies to HEV (anti-HEV). In Bali, anti-HEV was detected in 20% (54/276) of the tested population, in remarkable contrast with 4% (17/446) in Lombok and 0.5% (2/393) in Surabaya. On the other hand, antibodies to hepatitis A virus were highly prevalent in all three regions (95% in Bali, 90% in Lombok, and 89% in Surabaya). Although the majority of the population in Indonesia is Moslem, Balinese people are mostly Hindu and have a habit of consuming pork. Therefore, serum samples were obtained from the 99 farm pigs in Bali and tested for anti-HEV and HEV RNA. The sera from 71 pigs (72%) were positive for anti-HEV and a 2-month-old pig had detectable HEV RNA. The swine HEV isolate recovered from the viremic pig was named SB66-Bali. The SB66-Bali isolate was most closely related to the genotype 4 isolates from China, India, Japan, and Taiwan, but shared only 82.6-90.0% identity in the common 241-412 nucleotides within open reading frame 2 (ORF2). These results indicate that a presumably indigenous HEV strain(s) is circulating in Bali, Indonesia and that HEV infection may occur via zoonosis even in developing countries.

Does infection with hepatitis A virus provide protection against hepatitis E virus?

Hepatitis A virus (HAV) and hepatitis E virus (HEV) share some common epidemiologic features, but the dramatic age-related difference in their disease prevalences suggests that the immune response to HAV may provide some cross-protection against HEV.

New perspectives on hepatitis E

The infectious agent causing epidemic non-A, non-B hepatitis was identified in 1983 from a human challenge experiment. The novel hepatitis E virus (HEV) subsequently was cloned in 1990 and the genome sequenced. HEV transmission is highly endemic in Asia, the Middle East, and Africa. Fecal contamination of drinking water is the most common mode of spread. Although usually asymptomatic, HEV infection can cause fulminant hepatitis. Recent studies indicate that hepatitis E may be a zoonotic disease, with pigs and possibly rats serving as reservoirs for human infection. A recombinant HEV vaccine is currently in phase III clinical trials. The characterization of the major types of viral hepatitis during the last 20 years illustrates how modern genetic technology has revolutionized research in infectious diseases. Within less than two decades of the discovery of HEV, its epidemiology has been described, serologic tests have been developed, and a candidate vaccine has been evaluated in clinical trials.

First documented outbreak of hepatitis E virus transmission in Java, Indonesia

A suspected hepatitis outbreak occurred in Bondowoso District, East Java Province, Indonesia, in March-May 1998. An investigation was initiated in April 1998, involving a retrospective review of hospital records, a community-based cross-sectional study, and a health service-based case detection and household follow-up. Sera and epidemiological information were collected from 962 individuals: 235 from 3 outbreak-affected communities along the same rural stretch of river, 101 from community controls living distant from the river, 151 cases detected in health centres, 141 family members of the cases, and 334 subjects from neighbouring families. The prevalence of acute hepatitis E virus (HEV), based on anti-HEV IgM, total antibody (Ig) to HEV and polymerase chain reaction (PCR), was significantly (P < 0.00001) higher (52.4%) among the outbreak communities than among the community controls (3%). The background prevalence of HEV, based on anti-HEV IgG, was also significantly (P < 0.00001) higher (47%) among the outbreak communities than among the community controls (3%). None of the 476 sera screened for anti-HAV (hepatitis A virus) IgM was positive. These results indicate that HEV was the aetiological agent responsible for the outbreak. The overall attack rate (AR) for the 3 outbreak-affected communities surveyed was 19%, with AR determined on the basis of clinically recognized, acute jaundice illness. The usage of river water as primary source for bathing, human-waste disposal, and drinking purposes differed significantly (P < 0.00001) between the communities in outbreak areas and those in non-outbreak areas. There is no significant influence attributed to 'boiling water' on acute HEV. No climatic influences (flooding or drought) predisposed this instance of epidemic HEV transmission. This outbreak represents the first documented evidence of epidemic HEV transmission in Java, Indonesia.

Endemic infectious diseases of Afghanistan

The current crisis in Afghanistan has resulted in an influx of Western military personnel, peacekeepers, humanitarian workers, and journalists. At the same time, unprecedented numbers of internally displaced persons and refugees have overwhelmed much of the already fragile infrastructure, setting the stage for outbreaks of infectious diseases among both foreigners and local populations. This review surveys the literature concerning the infectious diseases of Afghanistan and south-central Asia, with particular emphasis on diseases not typically seen in the Western world.

Hospital-based diagnosis of hemorrhagic fever, encephalitis, and hepatitis in Cambodian children

Surveillance was conducted for three clinical syndromes (hemorrhagic fever, encephalitis, and hepatitis) in Cambodian children admitted to the National Pediatric Hospital in Phnom Penh from July 1996 through September 1998. Acute- and convalescent-phase sera, and cerebrospinal fluid, when applicable, underwent diagnostic evaluation for infections with Dengue virus (DENV), Japanese encephalitis virus (JEV), and Hepatitis A, B, C, and E viruses. Of 621 children admitted with hemorrhagic fever, 499 (80%) were confirmed to have either primary or secondary DENV infection. DENV rates were as high as 10.6/100 hospital admissions in September 1998. Of 50 children with clinical encephalitis, 9 (18%) had serologic evidence of JEV infection. Forty-four children had clinical hepatitis, most (55%) due to Hepatitis A virus (HAV). One patient had Hepatitis B virus, and no patients had hepatitis C or E. This study identified a large number of children with vaccine-preventable diseases (JEV and HAV).

Overview of Hepatitis E Virus

Hepatitis E virus (HEV) is an enterically transmitted virus usually presenting as an acute self-limiting disease. However, mortality increases dramatically from around 1% to 20% in pregnant women. HEV has been the cause of very large outbreaks of hepatitis in developing countries and is also responsible for a significant number of sporadic cases. It is clear that cases occur outside the endemic areas, and new isolates have been identified. HEV-like viruses have also been found in various animal groups, and it is likely that HEV can be regarded as a zoonotic infection. Preventative measures at the moment depend mainly on the provision of clean water supplies, although a vaccine is now undergoing clinical trials.

A review of hepatitis E virus

Hepatitis E virus (HEV) is a major cause of outbreaks and sporadic cases of viral hepatitis in tropical and subtropical countries but is infrequent in industrialized countries. The virus is transmitted by the fecal-oral route with fecally contaminated drinking water being the usual vehicle. Hepatitis resulting from HEV infection is a moderately severe jaundice that is self-limiting in most patients. Young adults, 15 to 30 years of age, are the main targets of infection, and the overall death rate is 0.5 to 3.0%. However, the death rate during pregnancy approaches 15 to 25%. Death of the mother and fetus, abortion, premature delivery, or death of a live-born baby soon after birth are common complications of hepatitis E infection during pregnancy. Hepatitis E virus is found in both wild and domestic animals; thus, HEV is a zoonotic virus. The viruses isolated from swine in the United States or Taiwan are closely related to human HEV found in those areas. The close genetic relationship of the swine and human virus suggests that swine may be a reservoir of HEV. In areas where swine are raised, swine manure could be a source of HEV contamination of irrigation water or coastal waters with concomitant contamination of produce or shellfish. Increasing globalization of food markets by industrialized countries has the potential of introducing HEV into new areas of the world. The purpose of this review is to cover certain aspects of hepatitis E including the causative agent, the disease, diagnosis, viral detection, viral transmission, epidemiology, populations targeted by HEV, and the role of animals as potential vectors of the virus.

Seroepidemiology of TT virus, GBC-C/HGV, and hepatitis viruses B, C, and E among women in a rural area of Tanzania

The seroprevalence and determinants of hepatitis B, C, and E virus infection, and of GBV-C/hepatitis G virus and TT virus infection were investigated among women from a rural area of northeastern Tanzania. High seroprevalence rates were found for TTV (74%), HBV (74%), and GBV-C/HGV (35%), whereas 7% of the women had evidence of HCV and HEV infection. The majority of TTV DNA sequences in the study population belonged to the genotypes 1 or 2. One sequence seems to represent a new subtype of genotype 4. The GBV-C/HGV sequences either belonged to the genomic Group 1b or to the recently described Group 4. In multivariate analysis, the detection of TTV DNA was associated significantly with a larger number of children in the household and with older age. A history of injections of contraceptive hormones was an independent risk factor for HCV infection. The findings on TTV are consistent with fecal-oral transmission, and recurrent infections may occur in adults.

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.