Hepatitis E virus resistant to most alcohol-based disinfectants

Alcohols and alcohol-based disinfectants are not strong enough to eliminate the hepatitis E virus (HEV), except for one commercial ethanol-based product that has phosphoric acid, a study has shown. This finding may help develop measures to reduce transmission in clinical practice.

“HEV showed a high level of resistance to alcohols and alcohol-based hand disinfectants,” the researchers, led by Patrick Behrendt from the German Centre for Infection Research, Hannover-Braunschweig, Germany, said. “The addition of phosphoric acid to alcohol was essential for virucidal activity against HEV.”

Behrendt and his team used a robust HEV genotype 3 cell culture model, enabling quantification of viral infection of quasi-enveloped and naked HEV particles. They used the primary isolate Sar55 in a faecal suspension for HEV genotype 1 infections.

In addition, the researchers performed standardized quantitative suspension tests using endpoint dilution and large-volume plating to determine virucidal activity of alcohols (1-propanol, 2-propanol, ethanol), WHO disinfectant formulations, and five different commercial hand disinfectants against HEV. They also did iodixanol gradients to explain the effect of ethanol on quasi-enveloped viral particles.

Naked and quasi-enveloped HEV showed resistance both to alcohols and alcohol-based formulations recommended by the WHO. However, one tested commercial hand disinfectant demonstrated virucidal activity against HEV, which could be attributed to the addition of phosphoric acid as an essential ingredient to its formulation. [J Hepatol 2022;76:1062-1069]

An earlier analysis revealed that the basic formulation of the product, with ethanol 55% and phosphoric acid 0.7% in combination with propan-1,2-diol and butan-1.3-diol, was responsible for its effectiveness against the stable poliovirus. [J Hosp Infect 2006;62:98-106]

“By utilizing a primary HEV-1 isolate (Sar55) we were able to demonstrate that this faecal-orally transmitted genotype was similarly resistant to the virucidal activity of ethanol,” the researchers said. [J Virol 2004;78:4838-4846]

Finally, Behrendt and colleagues found that ethanol and even nonactive alcohol-based disinfectants disturbed the quasi-enveloped structure of HEV particles but left the highly transmissible infectious naked virions intact.

Viral transmission

These findings must be put into perspective based on the different lifecycle and risk for infection of the distinct genotypes of HEV, according to Behrendt.

“HEV-3 and HEV-4 are zoonotic infections in humans, usually transmitted via contaminated food products. However, individuals with close contact to possibly infected animals are at increased risk of acquiring HEV infection,” the researchers said. [Zoonoses Public Health 2019;66:155-163]

“The use of gloves could reduce the risk of acquiring the infection in this setting. Therefore, it is very likely that virucidal hand disinfectants including an activity against HEV also protect from infection in this risk group,” they added. [BMC Infect Dis 2015;15:440]

On the other hand, HEV-1 and HEV-2 only circulate in humans and can lead to outbreaks in less-developed areas via waterborne transmission. Since HEV-1 is highly resistant to ethanol inactivation, developing hand disinfectants is necessary in addition to other measures in preventing transmission, according to the researchers.

“Therefore, we expect that the combination of different prevention measures (eg, Swiss cheese model) like vaccine, food safety, sanitary hygiene, and hand disinfectants will all contribute to the reduction of secondary infections independent of the HEV genotype,” said Behrendt and colleagues.