The major strains infecting humans are classified into 4 major genotypes with 2 distinct epidemiological profiles. In countries with poor environmental sanitation, HEV-1 and 2 (found exclusively in humans) are transmitted via the faecal–oral route and frequently trigger extensive waterborne outbreak. In industrialised countries, HEV-3 across the globe and HEV-4 mainly present in Asia are transmitted zoonotically from various animal reservoirs such as pigs, wild boars and deer. Most HEV infections are asymptomatic but even symptomatic hepatitis E is usually self-limiting and of variable severity
New Caledonia Island is a French overseas territory located in the southwestern Pacific Ocean. In August 2023, the New Caledonia Public Health Service was notified of a high number of HEV cases diagnosed at Noumea’s Hospital laboratory. This prompted epidemiological and virological investigations to identify the source of infection, led by Dr. Florence Abravanel from France Toulouse University Hospital. All patients presenting symptoms of acute hepatitis and testing positive for HEV IgM were enrolled in the study between August and December 2023. The cases were identified across the entire population on the Island.
HEV RNA was assessed in symptomatic patients, various food items. All 10 pig farms on New Caledonia Island were investigated. 127 symptomatic cases were reported. Hospitalisation was required for 29/127 patients (22.8%). There was no significant difference between the hospitalised patients and out-patients in terms of age, gender ratio, liver aminotransferase activity, HEV RNA concentration or reported symptoms apart from diarrhoea, which was more prevalent in hospitalised patients. The prothrombin percentage was lower (74% versus 86%, p=0.03) and comorbidities were more common in group I (80.7% versus 27%, p < 0.01). Three persons died (2.3%). Among the 100 HEV RNA-positive samples received at the French National Refence Centre for HEV, viral sequencing was possible for 76 samples. All strains were identified as HEV genotype 3 and 74/76 strains were grouped together (nucleotide identity: 98-100%). Full-length sequencing indicated a new HEV-3 subtype within HEV-3 subclade abk. The investigations of pork food providers showed that pig meat and livers had been imported from Australia in 2023. A high-sequence homology between New Caledonian HEV strains and Australian strains retrieved from the GenBank was found. Only genotype 3f strains were detected on the island’s pig farms. No food items tested positive for HEV RNA.
A seroprevalence study was also conducted on asymptomatic blood donors before and after the outbreak. The seroprevalence of HEV IgG and IgM in blood donors was 9.2% (9/98) and 0%, respectively, in 2020, rising to 17.3% (17/98) and 2% (2/98) in 2024. Even if blood donors are not representative of the general population of the island, but are only a proxy of the healthy population, we estimate that over 5,000 cases may have been asymptomatic in the New Caledonia outbreak. Although all previous large-scale epidemics in Asia and Africa were associated with HEV-1 or 2, the New Caledonia outbreak was linked to HEV-3. A high number of symptomatic cases were admitted to hospital with a case fatality rate of 2.3%.
Read the full article published in Hepatology. 2024 Aug 30. DOI: 10.1097/HEP.0000000000001081
