


Interestingly, not everyone is equally vulnerable to the virus, and whether you get sick or not may depend on your blood type.

Norovirus is hard to get rid of


As debilitating as the illness it causes can be, the norovirus particle is visually beautiful. It is a type of virus known as “non-enveloped” or “naked,” which means that it never acquires the membrane coating typical of other viruses, such as the flu virus. The norovirus surface is a protein coat, called the “capsid.” The capsid protects the norovirus’ genetic material.


To make things worse, only a tiny dose of the virus — as few as 10 viral particles — is needed to cause disease. Given that an infected person can excrete many billions of viral particles, it’s very difficult to prevent the virus from spreading.

Susceptibility to norovirus depends on blood type

When norovirus is ingested, it initially infects the cells that line the small intestine. Researchers don’t know exactly how this infection then causes the symptoms of the disease. But a fascinating aspect of norovirus is that, after exposure, blood type determines, in a large part, whether a person gets sick.


The same oligosaccharides on red blood cells also appear on the surface of cells that line the small intestine. Norovirus and a few other viruses use these oligosaccharides to grab onto and infect the intestinal cells. It’s the specific structure of these oligosaccharides that determines whether a given strain of virus can attach and invade.



More sugars can be attached to the H1-antigen to give the A, B or AB blood types. People who can’t make the A and B modifications have the O blood type.

Different strains of norovirus infect different people


If a group of people is exposed to a strain of norovirus, who gets sick will depend on each person’s blood type. But, if the same group of people is exposed to a different strain of norovirus, different people may be resistant or susceptible. In general, those who do not make the H1-antigen and people with B blood type will tend to be resistant, whereas people with A, AB, or O blood types will tend to get sick, but the pattern will depend on the specific strain of norovirus.

This difference in susceptibility has an interesting consequence. When an outbreak occurs, for example, on a cruise ship, roughly a third of the people may escape infection. Because they do not know the underlying reason for their resistance, I think spared people engage in magical thinking — for example, “I didn’t get sick because I drank a lot of grape juice.” Of course, these mythical evasive techniques will not work if the next outbreak is a strain to which the individual is susceptible.

Immunity to norovirus is short-lived



In general, these experimental vaccines produce good immune responses; the longevity of the immune response is now under study. The next phase of clinical trials will test if the vaccines actually prevent or reduce the symptoms of norovirus infection.

The Conversation

Patricia L. Foster is Professor Emerita of Biology, Indiana University.


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