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Norovirus in berries an emerging public health risk - EFSA

By Joe Whitworth+


Outbreaks associated with Norovirus in frozen raspberries and strawberries are an emerging public health risk, according to the European Food Safety Agency (EFSA).

The panel on Biological Hazards (BIOHAZ) said it is not known if in past incidents contamination occurred at minimal processing or during primary production.

Risk factors for berry fruits at primary production with Norovirus include environmental factors, in particular climatic conditions (e.g. heavy rainfall) that increase the transfer of Norovirus from sewage or sewage effluents to irrigation water sources or fields of berries.

Other concerns include the use of sewage-contaminated agricultural water, for irrigation or for application of agricultural chemicals such as fungicides and contamination and cross-contamination by harvesters, food handlers and equipment at harvest or post-harvest. 

Data collection and risk-based development of microbiological criteria to support improved control of Norovirus in frozen raspberries and strawberries should be considered as a priority, said the panel.

Attention should be paid to the selection of water sources for irrigation, agricultural chemicals (e.g. fungicides) and the avoidance of using or the ingress of water contaminated by sewage.

Production areas should be evaluated for hazards that may compromise hygiene and food safety, particularly to identify potential sources of faecal contamination.

If the evaluation concludes that contamination in a specific area is at levels that may compromise the safety of crops, intervention strategies should be applied to restrict growers from using this land for berry production until the hazards have been addressed.

Salmonella risk

Risk factors for the contamination of berry fruits at primary production with Salmonella includeenvironmental factors.

Other concerns were contact with animal reservoirs gaining access to berry fields, untreated or insufficiently treated manure or compost, contaminated agricultural water and contamination and cross-contamination by harvesters, food handlers and equipment at harvest or post-harvest.

There is insufficient evidence to justify establishing microbiological criteria for Salmonella for fresh or frozen berries, said the panel.

Mixing batches of frozen fruit, including different berry species, can present difficulties in traceability.

Interventions include water treatment and efficient drainage, gaseous ozone and heat processing.  

Limited data

There has been no routine or regular monitoring of berry fruits for Norovirus in most of the EU Member States and there is very limited prevalence data on Norovirus contamination of berries (not involved in foodborne outbreaks) in the peer-reviewed literature, said the panel. 

Appropriate food safety management systems including Good Agricultural Practices (GAP), Good Hygiene Practices (GHP) and Good Manufacturing Practices (GMP), should be primary objectives of berry producers.

This is the second opinion out of five and addresses the risk from Salmonella and Norovirus in berries.

The first opinion was published last year and looked at Salmonella and Norovirus in leafy greens eaten raw as salads.

Berries are often consumed as a perishable product receiving no or only minimal processing, those that are shelf-stable, having undergone heating or drying are outside the scope of the opinion.

The BIOHAZ panel concluded that: from 2007-2011, one Salmonellaoutbreak was reported which was associated with fresh raspberry juice.

Between 2007 and 2011, there were 27 Norovirus outbreaks associated with raspberries and one associated with strawberries.

It is not known if contamination occurred at minimal processing or during primary production.

The panel concluded that each farm environment represents a unique combination of risk factors that can influence occurrence and persistence of pathogens in berry production.

Source: EFSA BIOHAZ Panel (EFSA Panel on Biological Hazards), 2014

Online, DOI: 10.2903/j.efsa.2014.3706

Scientific Opinion on the risk posed by pathogens in food of non-animal origin. Part 2 (Salmonella and Norovirus in berries)

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