Soizick Le Guyader

Emergence of new norovirus variants on spring cruise ships and prediction of winter epidemics.

In June 2006, reported outbreaks of norovirus on cruise ships suddenly increased; 43 outbreaks occurred on 13 vessels. All outbreaks investigated manifested person-to-person transmission. Detection of a point source was impossible because of limited investigation of initial outbreaks and data sharing. The most probable explanation for these outbreaks is increased norovirus activity in the community, which coincided with the emergence of 2 new GGII.4 variant strains in Europe and the Pacific. As in 2002, a new GGII.4 variant detected in the spring and summer corresponded with high norovirus activity in the subsequent winter. Because outbreaks on cruise ships are likely to occur when new variants circulate, an active reporting system could function as an early warning system. Internationally accepted guidelines are needed for reporting, investigating, and controlling norovirus illness on cruise ships in Europe.

Viruses in Shellfish

Human pathogenic viruses enter the marine environment through several routes which include direct discharge of treated or untreated sewage effluents, unintentional discharges by urban and rural run-off, waste input from boats, and via rivers when wastewater discharges take place in fresh water. Current water treatment practices are unable to provide virus-free wastewater effluents, consequently human pathogenic viruses are routinely introduced into marine and estuarine waters. During feeding and under favorable hydrographic conditions, molluscan bivalves filter contaminants from polluted water and accumulate them within their edible tissues. A major public health concern posed by viruscontaminated bivalves is that shellfish are often eaten raw, such as oysters and clams, or improperly cooked, like most of other molluscan shellfish, just steamed for a few minutes. Although environmental virology started with the detection of poliovirus in water, other enteric viruses responsible for gastroenteritis and hepatitis have replaced enteroviruses as the main target for detection in the environment. Most shellfishborne viral outbreaks are restricted to norovirus and hepatitis A virus making them the main targets for bivalve virological analysis. In the present issue, updated extensive information on the state-of-the-art noroviruses and hepatitis A virus is provided in the first two papers. According the information provided by different outbreaks, the most common route for transmission is accidental contamination after heavy rainfall, when extra loads cause an overflow and release of untreated sewage into the aquatic environment. The environmental conditions leading to shellfish consumption-related outbreaks are described in a paper in the present issue. The inclusion of virus analysis in regulatory standards for viruses in molluscan bivalve samples must overcome several shortcomings such as the technical difficulties and high costs of virus monitoring, the lack of harmonized and standardized assays, and the challenge posed by the ever changing nature of viruses. Nowadays methods are available to detect, quantify, and characterize viral pathogens in molluscan shellfish to reduce the risks of shellfishborne virus diseases. However, standardization is necessary prior to virus methods can be considered for adoption within a regulatory framework. A European standardization working group is developing a two-part (quantitative and qualitative) standard method for virus detection in foodstuffs including shellfish which has the potential to be incorporated into EU legislation as a reference method. This development is described in another paper. Important trade exchanges of shellfish take place worldwide. Most countries have endorsed sanitary controls on live bivalve shellfish. In this issue, human enteric virus occurrence in shellfish from European markets is covered in one study after consulting various sources. The data demonstrate that viral RNA can be detected in shellfish from polluted areas, in depurated shellfish as well as in those for human consumption, without a good relation with the E. coli MPN that is in use for classification of growing areas and to determine whether shellfish products can be presented for human consumption. The reference guidelines, regulatory programs, and management practices to manage both recreationally and commercially grown shellfish developed in New Zealand A. Bosch (&) Dep. Microbiologia, Universitat de Barcelona, Avda. Diagonal 645, 08028 Barcelona, Spain e-mail: abosch@ub.edu