Beware the adenoviruses!

Enteric viruses are frequently associated with gastro-intestinal infections contracted from bathing waters. Mostly, the infections are minor; however these faecal-orally transmitted viruses can cause serious illnesses such as meningitis and hepatitis. Viruses such as adenovirus and norovirus are commonly implicated in waterborne diseases and can get into recreational bathing waters through faecal contamination; whether from treated or untreated sewage, farmland (manure) run-off or even from slaughterhouse waste. Despite the fact that such viruses have been found to be present in the faeces of infected individuals and in the water they had contact with, bathing water regulations still fail to take viral presence into account when determining water quality and still rely on bacterial indicators. This paper aimed to investigate the frequency of the virus groups in question (adenoviruses and noroviruses) across Europe and intended to identify a rapid method capable of testing for these viruses which could be used across Europe.

After marine and fresh water samples were filtered to concentrate potential viruses, a PCR based method was used to quantify their presence. Infectivity trials were also carried out to determine whether the viruses were replicating in culture and were thus infectious. The study also incorporated the traditional bacterial indicator method for comparison.

39.2% of samples were found to be positive for one or more of the target viruses and adenoviruses were more commonly found than noroviruses as they were present in 36.4% of samples compared to 9.4%, respectively. Freshwater samples also showed a higher frequency of viruses than marine samples which was attributed to their potential instability in saltwater; although noroviruses were more common in marine samples. The infectivity analysis showed that 47% of marine samples were positively infectious whereas only 20% of freshwater samples contained replicating viruses. Most interesting however are the comparison data between viral and bacterial indicators of pollution. For bacterial data matching to adenovirus data, 60.6% and 78.2% of samples had E. coli and intestinal enterococci concentrations below the ‘good’ threshold, respectively. For norovirus data, 59.6% and 73.1% of samples contained E. coli and intestinal enterococci concentrations below the ‘good’ threshold, respectively.

This suggests that viral infection should also be considered when regulating bathing water quality as waters that may be considered ‘clean’ according to bacterial indicators may actually still be harmful. In particular, testing for adenoviruses would be prudent as the study demonstrated their hardiness and prevalence within the environment, as well as their association with faecal pollution. Furthermore, this study also demonstrated a method which could be utilised internationally for viral indicator testing, although the viruses would need to be quantitatively measured, not just found to be present or absent as not all viruses were infectious. Overall, the study provides compelling evidence that viruses need to be recognised as indicators of pollution (but we all knew that anyway!) and, despite being complicated in places, these findings go some way to help modify European bathing water policies.

A review of: Wyn-Jones AP, Carducci A, Cook N, D’Agostino M, Divizia M, Fleischer J, Gantzer C, Gawler A, Girones R, Ho¨ller C, de Roda Husman AM, Kay D, Kozyra I, López-Pila J, Muscillo M, São Jose Nascimento M, Papageorgiou G, Rutjes S, Sellwood J, Szewzyk R, Wyer M. (2011) Surveillance of adenoviruses and noroviruses in European recreational waters. Water Research 45: 1025-1038.