Mucosal Immunity

The “Ferrari of viruses” is having a banner season. Norovirus, which races through cruise ships, homes, and long-term care facilities, is experiencing a remarkable winter surge in the Northern Hemisphere, sending large numbers of people racing to the bathroom and many others to the hospital, and in rare cases, proving fatal. In the United States, for example, 91 outbreaks of the intestinal virus occurred in the first week of December 2024, far above the previous maximum, 65, for the same week between 2010 and 2024. And levels of its genes in U.S. wastewater are an order of magnitude above last year. “The early data for the early part of the season is certainly supporting that we’re going to have a pretty intense norovirus year,” says Lisa Lindesmith, who studies the virus at the University of North Carolina (UNC) at Chapel Hill. Some of the surge may be due to a new variant of the virus, unfamiliar to many people’s immune systems, and the resumption of cruises and other gatherings that the COVID-19 pandemic interrupted. And there’s no vaccine anywhere in sight: The most advanced candidate just failed a key trial and others won’t be ready for several years. Norovirus thrives in cold climes, causing explosive diarrhea and vomiting that typically only last for a day. But several weeks after people recover, they can still shed the virus, and it can remain infectious for long periods on surfaces. It’s notoriously resistant to many disinfectants, and studies in adult volunteers have shown just a trace of virus is enough to sicken a person. Oysters are also a source of infection, because the filter-feeding mollusks concentrate the virus from contaminated water in their tissues. U.S. health officials issued several warnings about infected oysters in December, and France has banned oyster harvesting in certain regions because of norovirus outbreaks.

For most people the virus is a rapidly passing misery that creates the wrong kind of unforgettable memories from a wedding or a holiday gathering. But, “It can be pretty severe,” says Mary Estes, a virologist at the Baylor College of Medicine who is a leading researcher in this small field. Although norovirus-related mortality is low in wealthy countries, it kills an estimated 200,000 young children in the developing world each year. Even in the U.S., it’s the leading cause of hospitalization for diarrheal disease, hitting young children and the elderly particularly hard. Immunocompromised people, particularly cancer patients on chemotherapy or transplant recipients taking antirejection drugs, can have chronic infections that last for months or even years. Many sickened people also miss work, globally leading to an estimated $60 billion in annual losses. Given that symptoms quickly resolve in most cases, few people seek care, but in the U.S., reports of norovirus-related outbreaks—two or more illnesses from a common source—this winter promise to far outstrip the 2500 typically seen. Cruise ships are being hit hard, too. In the United Kingdom, labs that test for the virus reported 63% more positive samples in the last 2 weeks of 2024 than the average, and hospitalizations were up 11%.

Albert Kapikian at the U.S. National Institutes of Health discovered the first norovirus in 1972 from an outbreak of “winter vomiting disease” that occurred at an elementary school in Norwalk, Ohio—hence the “noro” in the name. Scientists have since described more than 30 major variants that circulate in humans, distinguished by changes in their surface protein, VP1, which is the main target of antibodies that can “neutralize” it. “This virus is really good at getting around antibodies,” says veteran norovirus researcher Christine Moe of Emory University. “I used to think it was the most successful pathogen until COVID came along.” The world had four massive waves of norovirus between 2002 and 2012—“the most pandemics of any virus in the 21st century,” says UNC’s Ralph Baric, who has long studied the pathogen. Each erupted when a new norovirus variant replaced the dominant one. But since 2012, a set of related variants called GII.4 has held sway. “One of the hottest topics in norovirus research is why, after having those really frequent replacement events, has that process slowed down?” says Lindesmith, who works in Baric’s lab. A change that could help explain this winter’s surge in cases is the success of GII.17, a variant that has circulated at low levels for decades. GII.17 began to rise in the U.S. and six European countries last year, a 26 September 2024 paper in Eurosurveillance reported. According to the U.S. Centers for Disease Control and Prevention, 70% of 56 viral isolates sequenced between 1 September and the end of the year belong to the GII.17 lineage. The U.K. and the Netherlands are also seeing GII.17 dominate. Whether it will end GII.4’s 12-year reign as the dominant variant won’t be clear for many months.

Helicobacter pylori (H.p.) is a Gram-negative bacterium endowed with gastric tropism. H.p. infection is widely spread throughout the world, accounting for various pathologies, such as peptic ulcer, gastric cancer, mucosa-associated lymphoid tissue lymphoma, and extra-gastric manifestations.

Stanford University scientists’ findings in mice could translate into a radical, needle-free vaccination approach that would also eliminate reactions including fever, swelling and pain.

Norovirus Vaccines: Unlocking the Next Frontier in Global Health

Did you know norovirus causes over 677 million cases of gastroenteritis annually, costing $60…