"The winter vomiting bug is highly infectious and fast to evolve, but can we learn anything from groups of people who are unusually immune to the virus?
"Norovirus doesn't do that," she says. "It's just a little protein bomb, and so things like hand sanitizer can't kill it, while it's still able to move from cell to cell."
The reason for this is because norovirus largely prefers to enter the cells in the small intestine via antigens, molecular gateways called oligosaccharides, which are made from an assortment of different sugars. Both GII-4 and many other norovirus strains require one particular oligosaccharide, called the H1-antigen, in order to infect a person.
According to Robert Atmar, a virus expert and professor at Baylor College of Medicine in Houston, Texas, this information could in future aid the development of better antivirals against norovirus strains. "There are studies being done to see if taking advantage of the interaction between noroviruses and the antigens on cells might be targeted for the development of a therapeutic," he says.
However, this work is complex because of the speed with which noroviruses adapt and change their genetic material, meaning that some strains have still found a pathway to infect individuals who are relatively resistant.
"I'm a non-secretor myself," says Foster. "It means you're somewhat resistant but not completely, as norovirus evolves extremely rapidly."
She predicts that even non-secretors may become more susceptible to variants of GII-4 with time, as this strain of norovirus figures out different pathways into the body.
"These cell culture models may be helpful in vaccine efforts by demonstrating that immune responses generated after vaccination kill or inactivate the virus by neutralizing its infectivity," says Atmar.
"We're still learning a lot about norovirus vaccines and how they might protect," says Atmar. "We know that administration of virus-like particle (VLP)-based vaccines via the nose or by intramuscular injection can lead to protection from illness. mRNA vaccines may allow increased numbers of strains to be included. I think all will likely be effective, and the relative effectiveness will depend on other factors we are still learning about, including breadth of the immune response after vaccination, duration of immune response, and role of past infection and genetic makeup on an individual's response and protection."
"Vaccines produced using our approach will need regular updates to address the challenges of rapid virus evolution and the potential emergence of new norovirus genotypes as predominant strains in the future," he says.
However, Atmar remains more optimistic, saying that we need to wait until the results of much larger trials before any firm conclusions can be made on potential vaccine durability.
"The results of one of the studies for the VLP vaccine being pursued by HilleVax suggests that it can also protect against disease caused by the GII-2 strain when the vaccine contained GI-1 and GII-4 strains," he says. "So, we don't know whether it'll be like influenza or Covid [where regular boosters are required], or that it might be more like RSV where strain updates are not needed."
But if we can develop at least one vaccine in the years to come, it will represent a major step forward in humanity's ongoing battle with norovirus.
* This article was originally published on 7 March 2024. It was updated on 31 December 2024 to include data on the latest outbreaks of norovirus in the US.