Detection of tomato brown rugose fruit virus in environmental residues: the importance of contextualizing test results
Tomato brown rugose fruit virus (ToBRFV) is regulated as a quarantine pest in many countries worldwide. To assess whether ToBRFV is present in cultivations, plants or seed lots, testing is required. The interpretation of test results, however, can be challenging. Real-time RT-PCR results, even though considered "positive", may not always signify plant infection or indicate the presence of infectious virus, but could be due to the presence of viral residues in the environment. Here, case studies from the Netherlands, Belgium, and the United Kingdom address questions regarding the detection of ToBRFV in various settings, and the infectiousness of ToBRFV positive samples. These exploratory analyses demonstrate widespread detection of ToBRFV in diverse samples and environments. ToBRFV was detected inside and around greenhouses with no prior history of ToBRFV infection, on different materials and surfaces including those that were untouched by individuals, plants, or objects. This suggested the dispersal of viral residues through aerosols. ToBRFV or its residues were more often detected in areas with nearby tomato production yet were also found in a wider environment extending beyond infected crops. Given that ToBRFV originating from environmental contamination may or may not be infectious, adds complexity to decision-making in response to positive test results. Contextual information, such as the origin of the sample and the likelihood of residues from prior cultivations and/or the broader environment, is important for interpreting test results. A nuanced approach is crucial to correctly interpret ToBRFV test results, necessitating further research to support risk assessment.