Tracing Outbreaks on Cruise Ships.

• Position: STOMACH VIRUSES - Norovirus and rotavirus

Researchers have found that a group of viruses that causes severe stomach illness--including the one famous for widespread outbreaks on cruise ships--gets transmitted to humans through membrane-cloaked "virus clusters" that exacerbate the spread and severity of disease. Previously, it was believed that these viruses only spread through individual virus particles.

The discovery of these clusters, the scientists say, marks a turning point in the understanding of how these viruses spread and why they are so infectious. This preliminary work could lead to the development of more-effective antiviral agents than existing treatments that mainly target individual particles.

The researchers studied norovirus and rotavirus--hard-to-treat viruses that are the most-common cause of stomach illness, or gastroenteritis, that afflicts millions of people each year. The viruses cause symptoms ranging from diarrhea to abdominal pain and sometimes can result in death, particularly among young children and the elderly. Their highly contagious nature has led to serious outbreaks in crowded spaces throughout many communities--most notably on cruise ships and in daycare centers, classrooms, and nursing homes. Vaccines against rotavirus now are available and routinely are given to babies.

"This is a really exciting finding in the field of virology because it reveals a mode of virus...