Study sheds new light on human noroviruses

Human noroviruses are said to be the single biggest cause of gastroenteritis in the industrialised world and are associated with foodborne disease and rapid person-to-person transmission.

Unfortunately, unlike other viruses, human noroviruses cannot be grown in the laboratory so scientists have struggled to understand how best to inactivate them.

New research carried out in the UK by Leatherhead Food Research, the Department for Environment Food and Rural Affairs, a consortium of industrial companies and the Health Protection Agency, has shed new light on the behaviour of these pathogens.

The scientific team led by Dr Angus Knight firstly developed and tested a new molecular method for measuring virus inactivation (without the need to grow virus) using a distantly related cat vaccine virus that is safe to use and can be grown in the laboratory.

The team then applied the same molecular approach to human noroviruses in order to predict their behaviour. Surprisingly, the noroviruses were much more resistant to temperature and a range of disinfectants and hand sanitisers compared with other viruses. Interestingly, when the cat vaccine virus was added to human norovirus samples, the cat virus became much more resistant and behaved more similarly to the human noroviruses.

The findings suggest that the increased resistance of the human noroviruses is derived from their natural human faecal environment. This increased resistance may explain why these organisms persist in the environment and are difficult to control, leading to prolonged outbreaks of disease.

Further work is now required to develop more effective hygiene control measures for human norovirus.