Several viruses behind winter vomiting disease
A child with diarrhoea in Leon, Nicaragua
The same virus that plagues many Swedes every winter with vomiting and diarrhoea each year kills an estimated 200 000 children, the majority in developing countries. Researchers at Linköping University have now mapped the subspecies of the norovirus which usually causes the disease.
The results of studies in Sweden and Nicaragua are now presented in a doctoral thesis by Johan Nordgren, doctoral student in virology at LiU. They suggest that it is mostly variations of a particular subspecies, GGII.4 that causes illness during the main disease period - winter in Europe and the rainy season in tropical countries. The timing of the main disease period has led to the disease often being referred to as winter vomiting disease. The second half of the year sees a reduction in the incidences of GGII.4 and other subspecies of norovirus begin to circulate.
High concentrations of these subspecies were observed in waste water in the summer, and it was discovered that some of them can infect people who are usually resistant to the winter species, GGII.4; winter vomiting disease.
- Our results provide a greater understanding of virus occurrence and pathways and hopefully lead to better preventive measures against winter vomiting disease in the future, says Johan Nordgren.
Each year up to 250 million people globally succumb to winter vomiting disease. Large outbreaks occur in closed environments such as hospitals, nursing homes, child day-care centres and cruise ships where the virus can easily spread from person to person. About one fifth of the population of Europe is usually resistant to winter vomiting disease but this resistance is only mapped to a few of all the subspecies.
To obtain information on which of the subspecies of norovirus circulate and cause disease, the researchers developed a sensitive molecular biological method that can detect and measure the concentration of norovirus in patient samples and sewage. This method can also distinguish between the different sub-groups of the virus.
In samples from Nicaragua , the team observed that norovirus caused 15 percent of the diarrhoea in children so severe it had to be treated in hospital. The incidence of diarrhoea fluctuated throughout the year and the major peaks were due to the development of new variants of the species GGII.4, which seem to be more infectious with worse symptoms.
A recent outbreak of winter vomiting disease in Jönköping, Sweden was caused by the infection spreading through pizzas. However it was not the first time this happened in Jönköping. At a conference in October 2007 many of the participants fell ill with vomiting and diarrhoea, LiU researchers subsequently discovered that food served was contaminated with a rare subspecies of norovirus.
Surprisingly, it appeared that many people who became ill would normally have been resistant to winter vomiting disease. A variety of genetic factors were investigated but none provided total protection against infection, however people with blood group B succumbed to a lesser extent than those with blood group A or O.
The thesis is presented on Thursday, April 23, 2009 at 13:00 in Berzelius Hall, Campus U.S., Linköping. Opponent is Professor Annalarua Carducci, Pisa, Italy.
Last updated: 2009-06-03