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Noroviruses and hepatitis A viruses on frozen berry fruits

The highest numbers of cases of norovirus and hepatitis A disease occur seasonally during the winter months. In addition to fecal-oral transmission, contaminated food can cause infections.

Noroviruses have a high heat and cold tolerance (approx. 60 °C to -20 °C). 10-100 virus particles are already sufficient to cause an illness. Therefore, norovirus infections spread very quickly and are often the cause of outbreaks in hospitals, nursing homes or other community facilities such as daycare centers or schools. The most severely affected are one-year-old children (295 cases /100,000 inhabitants) and the group over 79 years (122 cases /100,000 inhabitants), as described by the Robert Koch Institut in the Infektionsepidemiologisches Jahrbuch for 2020 (German only).

Characteristic of infection with norovirus is severe vomiting and diarrhea. Hepatitis A is a disease of the liver caused by hepatitis A viruses. In severe cases, hepatitis A viruses can lead to liver inflammation. As with norovirus, the route of transmission is through contaminated food and drinking water.

In addition to mussels and oysters, fruits and vegetables can also be affected. A simultaneous analysis for norovirus and hepatitis A is therefore advisable.

Current case numbers in Germany

In 2020, 64% fewer norovirus infections were reported to the RKI (28,511 cases in total). This corresponds to an incidence of 34 cases/100,000 population. This shows a significant decrease compared to the previous year (95 cases /100,000 inhabitants). Presumably, this is due to the strengthened hygiene and distance rules to contain the COVID-19 pandemic. (RKI)

However, since 2011, according to the RKI, only one clinical laboratory-confirmed norovirus case meets the reference definition. Therefore, no data are available on confirmed illnesses without laboratory findings. This leads to a significant underestimation of the actual number of cases.

Viruses on frozen berry fruits

Frozen fruits are a popular substitute for fresh fruit, especially during the winter months. However, because these products are usually used raw, these foods are particularly susceptible to the spread of infection. On several occasions in recent years, outbreaks have been traced to frozen soft fruits such as strawberries and raspberries. In most cases, contaminated water is the reason for virus contamination of these products.

Analytical detection of noroviruses and hepatitis A viruses

DIN EN ISO 15216-2:2019 describes sample preparation and detection of noroviruses and hepatitis A by RT real-time PCR. Following the ISO method, CONGEN has developed the SureFast® Norovirus + Hepatitis A 3plex detection kit (Art. No. F7124) and established it in our own service laboratory for analysis.

In addition to the direct detection of noroviruses and hepatitis A, the detection kit contains a verification system for possible PCR inhibitions. By using appropriate control samples, a detection system is thus available that enables unambiguous and sensitive results.

In the CONGEN ServiceLab, frozen berry fruits are regularly tested for these pathogens. Participation in ring trials ensures reliable and sensitive detection.

If you are interested in further information and would like to receive a quotation, please contact us.