Australia has one of the safest blood supplies in the world – an important contribution to maintaining safety is active research to identify emerging risks. The Blood Service recently published the results of a large hepatitis E virus (HEV) prevalence study in the journal Vox Sanguinis. The study aimed to determine the frequency of HEV infection in Australian donors, and the associated transfusion-transmission (TT) risk.
Hepatitis E is a liver disease caused by the hepatitis E virus (HEV). It is typically transmitted via the faecal-oral route and is predominately spread by eating or drinking contaminated food or water. The highest rates of hepatitis E infection occur in regions where there is poor sanitation and sewage management that promotes the transmission of the virus. For example, hepatitis E is common in Central and South-East Asia, North and West Africa and Mexico.
In developed countries, there is a wide variation in the number of cases of HEV in particular countries. Where infections occur, cases are typically caused by ingesting undercooked pork or pork products derived from infected animals. Transmission of the virus through blood transfusion is also possible and has been demonstrated in multiple countries, including one probable case in Australia. Infection sometimes causes symptoms such as vomiting, diarrhoea, jaundice and liver swelling, but in developed countries the majority of HEV infections are asymptomatic and therefore not effectively managed by donor exclusion criteria. HEV can lead to chronic infection in immunosuppressed patients such as transplant recipients, but there is treatment for chronic infection that will result in cure in the vast majority of patients.
The Blood Service doesn’t routinely test for HEV because, although common worldwide, it is not thought to be commonly acquired in Australia, with approximately 30 new cases reported each year. However, HEV infection has increased in prevalence in many developed nations, and some countries have implemented HEV RNA screening to manage transfusion-transmission (TT) risk. A recent study, led by Dr Helen Faddy from the Research and Development team in collaboration with colleague Dr Veronica Hoad from the Donor and Product Safety Unit, investigated the frequency of HEV infection in Australian donors.
“We wanted to find out whether any of our whole blood donors were infected with the hepatitis E virus,” explained Dr Faddy, “This information will be used to assess the risk of transmitting HEV through blood transfusion, and help us decide whether we need additional controls to keep the blood supply safe.”
“We collected an extra plasma sample from 74,131 whole blood donors across Australia between May and November 2016. We tested for the virus in the donor blood samples by looking for its genetic material (RNA),” said Dr Faddy, describing the study.
From the large group of blood donors, only one HEV RNA positive donation was detected, with an estimated viral load of 180 IU/ml, which is below the viral load typically associated with TT. Using a transmission-risk model, the Blood Service estimated the risk of an adverse outcome associated with TT-HEV of approximately 1 in 3.5 million components transfused. The results showed that the risk of collecting a HEV infected whole blood donation in Australia is low, and much lower than the risk in other developed countries, where selective screening has been implemented.
As a result of such low prevalence, complications due to TT are expected to be exceedingly rare. Therefore, the Blood Service has concluded that HEV blood donor screening is not currently warranted in Australia. Feedback from clinicians and government stakeholders supported this conclusion. The vast majority of confirmed HEV infections in Australia are acquired through overseas travel, especially to developing countries. Blood donors are generally ineligible to donate fresh components on return from these countries because of deferrals related to the risk of malaria.
All cases of suspected TT-HEV should be reported to the Blood Service for further evaluation. The Blood Service will continue to monitor the risk of HEV in Australia and will review our assessment if required.