Food virus testing: ask the right question before interpreting the result
Testing food for viruses is very different from routine bacteriological testing. ViroSafety provides independent advice on testing strategy, ISO 15216 and interpretation of laboratory results.
When can food-virus testing be useful?
Incident & outbreak investigations
Testing may contribute evidence when considered alongside epidemiology, sampling location, timing and the circumstances of the incident.
Verification & investigation
It may help address a defined question involving a supplier, process, product, environment or research exercise.
Sampling matters
The value of a result depends heavily on the sampling plan, food matrix, timing and how representative the tested sample is.
Detection is not the same as infectivity
ISO 15216 provides standardised molecular methods for detection and quantification of norovirus and hepatitis A virus in specified food matrices using real-time RT-PCR. These methods detect viral RNA. A positive molecular result does not, by itself, demonstrate that infectious virus is present.
What does the result actually tell you?
A positive result
May provide important evidence of contamination. Interpretation should consider the method, controls, result format, sample type, sampling location, epidemiological evidence and the original reason for testing.
A negative result
Applies to the sample tested. It should not automatically be taken as proof that an entire batch, production environment or supply chain is free from virus. Contamination may be heterogeneous.
Putting laboratory findings into context
ViroSafety can help organisations assess whether a testing approach addresses the question being asked and understand what the laboratory findings mean in practice. Advice can include norovirus and hepatitis A results, ISO 15216, recovery and process controls, RT-PCR findings, sampling considerations and the limitations of molecular detection.