Seaweed: Norovirus contaminations?

29 March, 2017


pcr detection for viruses detection: seaweed contamination with norovirus?

Norovirus (and other waterborne viruses) can enter ocean habitat from sewage outflows or through waste discharged. Noroviruses are highly contagious. Good Aquaculturing Practice, Good Hygiene Practice, and Good manufacturing Practice are key to prevent foodborne virus outbreaks.  

Definition of Seaweed

  1. A mass or growth of marine plants

  2. A plant growing in the sea, especially: a marine alga (as a kelp)

Marine macroalgae (seaweeds) are plant-like organisms that generally live attached to hard substrata in coastal areas. They belong to three different groups :

  • brown algae
    red algae
    green algae


Norovirus outbreaks with seaweed

After a scientific publication by Korea describing an outbreak with seasoned green seaweed, a more recent news from Japan confirms a norovirus outbreak due to kizami nori from Japan.

1/ In South Korea, seasoned green seaweed and norovirus

In February 2012, an outbreak of gastroenteritis was reported in school A; a successive outbreak was reported at school B. A retrospective cohort study conducted in school A showed that seasoned green seaweed with radishes was significantly associated with illness. Multiple norovirus genotypes were detected in samples from students in schools A and B. Green seaweed was assumed to be linked to these outbreaks. 

2/ In Japan, kizami nori and norovirus

In February 2017, 1,098 students at the Tachikawa City schools were affected by the outbreak, linked to “Nori” 刻み海苔 dried laver seaweed (blamed for food poisoning outbreaks at schools in Tachikawa, western Tokyo, as well as Gobo and Hidakagawa, both of which are in Wakayama Prefecture).They presented with symptoms of vomiting and abdominal pain. Norovirus has been detected in at least one of the patients and the strain matched the strain found in the shredded seaweed samples.


Production of Japanese Nori.

An Example:

Can Norovirus be deactivated in seaweed?

Norovirus is unique, and different from surrogates usually used in studies . A study investigated the effects of gamma radiation (3-10 kGy) upon the inactivation of murine norovirus-1 (MNV-1), a human norovirus (NoV) surrogate, on the edible green and brown algae, fulvescens (Capsosiphon fulvescens) and fusiforme (Hizikia fusiforme), respectively,


Adhesion of norovirus to vegetal surfaces

The attachment of these pathogens to foodstuff and food-contact surfaces is an important mechanism in the human contamination process. The results of a study (Bacterial Surface-Displayed GII.4 Human Norovirus Capsid Proteins Bound to HBGA-Like Molecules in Romaine Lettuce) indicated that histo-blood group antigen-like molecules in LE or VE were involved in the binding of the surface-displayed HuNoV proteins to romaine lettuce.

What should seaweed producers do?

It is important that producers and processors, as well as importers and retailers of seaweed take into account the viral risk in their HACCP plan, and identify the various critical control points (CCP), where Norovirus could have been in contact with the sea vegetable. Processes should be evaluated to verify that they can inactivate norovirus, a major cause of food contamination worldwide. Good Agricultural Practice should be set into place to prevent any cross-contamination. Scientific Opinion on the risk posed by pathogens in food of non-animal origin. Part 2 (Salmonella and Norovirus in leafy greens eaten raw as salads)


Norovirus Detection Methods in Seaweed

The ISO 15216 Standard, an horizontal method for the detection of foodborne viruses in food matrices, covers several specific matrices, including vegetable in a form of a leaf. Norovirus GI and norovirus GII presence or absence can be evaluated using PCR real time detecion, after several steps including sample preparation and elution. 


Learn more about Food- and Water-borne viruses



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