Hepatitis E virus (HEV) is a virus that infects the liver to cause inflammation (hepatitis). It is mainly transmitted by either the faecal-oral route, where faeces contaminates water or food, or from consuming undercooked pork products. In addition, transmission has been documented to occur by organ transplantation and blood transfusion. In the majority, people who are infected do not have any symptoms. If symptoms occur they typically include fever, weakness, tiredness, nausea, vomiting and jaundice. There are four main genotypes of HEV that have different routes of transmission and differing characteristics. In immunosuppressed patients genotype 3 can cause chronic infection and the infection can be severe.
Cases of diagnosed HEV are uncommon with an average of only approximately 30 cases a year in Australia. The vast majority of infections notified in Australia are from overseas acquired infections where outbreaks occur in developing countries such as Asia, India and Africa due to contaminated water which is associated with genotype 1 and 2. In developed countries, such as Australia, locally acquired cases are predominately genotype 3, which is associated with consumption of undercooked pork. Although HEV remains a rarely diagnosed illness in the community, there has been increased recognition world-wide that healthy people may have higher asymptomatic infection rates than previously thought. In particular studies of asymptomatic blood donors in developed countries have detected a rate of asymptomatic viraemia that can result in transfusion-transmission.
In the UK, their Advisory Committee on the Safety of Blood, Tissues and Organs (SaBTO) has recently recommended that HEV blood donor screening for blood components given to patients at higher risk of severe infection such as transplant patients be implemented. Australian Red Cross Lifeblood (Blood Service) is considering the risk in the context of the disease patterns that occur in Australia. Australia has a different pattern of HEV disease compared to the UK which is
• considerably less HEV case rates compared to UK HEV case rates
• the UK has a much higher proportion of locally acquired cases whereas the majority of cases in Australia are acquired overseas
• a preliminary study of infections detected in Australian blood donors is considerably less than the UK blood donor rate.
This suggests that HEV poses a considerably lower risk in Australia compared to the UK.
Hepatitis E is not routinely tested for in the blood donation process. However, blood donors are not permitted to donate if unwell and are asked to notify the Blood Service should they become unwell post-donation. If blood donors have a history of hepatitis they are not permitted to donate for 12 months. Blood donors who have travelled to developing countries where most outbreaks occur are not permitted to donate fresh blood components during the risk period because of other infectious diseases that result in a temporary deferral from blood donation. Therefore most cases diagnosed in Australia would not be permitted to donate fresh blood components and this is different from the case in the UK.
Given the small number of cases of hepatitis E in Australia and the rigorous donor selection process, the risk of transmission is low, but is not zero. In response to HEV, the Blood Service has completed an initial assessment of HEV to consider whether any additional measures such as increasing donor deferrals, conducting further research on the risk in blood donors or assessing if targeted testing is an option. Whilst a final decision has not been made, preliminary results of this assessment indicate that transfusion-transmission is likely to be a rare event and Australia’s blood supply is at considerably lower risk of HEV than other international blood services. However, given the uncertainty of the rate of infection in Australia, the Blood Service suggests clinicians consider the diagnosis of HEV in immunosuppressed patients and report back to the Blood Service if the diagnosis is confirmed and the patient has received fresh blood components.