An outbreak of gastrointestinal illness in Catalonia, Spain caused 4,136 cases in April 2016.
Infectious viral titer estimates were 33–49 genome copies/L for genotype I and 327–660 genome copies/L for genotype II.
Aigua del Pirineu SL bottled water from the Font D´Arinsal de Andorra spring and it was distributed by Eden Springs España SAU.
In April last year, more than 6,000 containers were recalled that had been distributed to 925 companies.
Investigation pointed to bottled water
The Public Health Agency of Catalonia (ASPCAT) investigation led to an association with drinking bottled spring water from office water coolers.
The cause of water contamination is not clear but the high number of affected people from 381 offices that received water coolers and the different genotypes found in patients’ fecal specimens, point toward sewage pollution of the spring aquifer, said researchers.
Aquifer pollution was acknowledged by the Andorra Ministry of Health and Welfare and further use of the spring was banned.
“This large outbreak suggests that the management of microbial risks of commercially produced mineral waters, universally based solely on bacterial parameters, could benefit from additional analysis for relevant viral pathogens such as norovirus,” said researchers.
“However, the substantial costs incurred in developing, enhancing, and managing virus surveillance systems call for a balanced approach to keep both the cost and the time required for the analyses within feasibility limits.”
In past work several brands of mineral water were reported to contain norovirus but the findings were later attributed to laboratory contamination with control reagents.
Quantitative detection of norovirus in bottled water
Researchers took samples from four 19L water coolers in two offices in the Barcelona metropolitan area, from which affected people had drunk.
They collected samples one and two from two water coolers in one office, from which 36 cases had been reported.
A private company provided samples three and four, from two water coolers in a different office with an unknown number of cases.
Researchers detected high RNA levels for norovirus GI and GII, around 103 and 104 genome copies/L, in two of the four water cooler samples concentrated by glass wool filtration and polyethylene glycol precipitation.
Because molecular methods cannot tell between infectious and non-infectious particles, they predicted infectivity of norovirus in the concentrated samples by treating them with the nucleic acid intercalating dye PMA propidium monoazide; (50 µmol/L) and Triton X surfactant (0.5%) before RT-qPCR.
The team then estimated infectious levels in the two positive samples were 49 and 327 genome copies/L for norovirus GI and 33 and 660 genome copies/L for norovirus GII.
“We hypothesize that the spring water was contaminated by all four strains (GI.2, GII.2, GII.4 and GII.17) but levels of viral contamination for each genotype were not homogeneous in all bottled coolers.”
“Norovirus in Bottled Water Associated with Gastroenteritis Outbreak, Spain, 2016”
Authors: Albert Blanco, Susana Guix, Noemí Fuster, Cristina Fuentes, Rosa Bartolomé, Thais Cornejo, Rosa Maria Pintó and Albert Bosch