Can You Get Norovirus Twice? Doctor Explains the Risks of Reinfection.

Norovirus is an extremely contagious organism. Until this moment, no vaccine can protect you from getting norovirus twice. Today I will answer all your questions about norovirus reinfection: is it possible to get it more than once in a short period, and what factors contribute to getting norovirus twice?

Quick summary:

Can you get norovirus twice?

Absolutely!

According to the Center For Disease Control And Prevention, it’s entirely possible to experience multiple bouts of norovirus infection throughout your lifetime. Even if your body has developed antibodies to the norovirus, it doesn’t guarantee immunity unless you’ve been infected by the same strain of the virus multiple times (source).

There are several risk factors associated with contracting norovirus more than once, such as (source):

• Advancing age,
• Chronic illnesses that weaken your immune system, or
• Repeated exposure to high doses of the virus.

Since the introduction of the rotavirus vaccine, norovirus has become the leading viral cause of gastroenteritis in adults and children.

Unlike rotavirus, there’s no vaccine for norovirus. The immune response to this virus is complex, not fully understood, and, unfortunately, incomplete.

The CDC explains that you can contract norovirus more than once by being infected with a different strain or reinfected with the same strain (source).

Several factors contribute to contracting norovirus more than once. Apart from the viral factors, the immune response to norovirus is complex and incomplete.

More: Norovirus stool color changes and when to worry.

How fast can you get norovirus twice?

As previously mentioned, having had norovirus gastroenteritis doesn’t mean you’re immune. It’s possible to contract norovirus again after a few months or, less commonly, within a few days or weeks.

Can you get norovirus twice in the same season?

In the USA, norovirus is the leading cause of diarrhea outbreaks, which typically occur between November and April. So yes, it’s possible to contract norovirus twice in the same season.

Even though some people can develop immunity and produce antibodies against norovirus, there’s no guarantee against reinfection.

This immunity is incomplete and requires more than one Infection to develop immunity to a specific strain of norovirus.

The CDC also states that antibodies aren’t the only immunological factor that fights norovirus. Factors like “the innate immune response” and genetic differences may also play a role.

The exact duration of immunity against norovirus is still unknown. This may explain why people of all ages contract norovirus during outbreaks (source).

Can you get norovirus twice in one month or the same week in a row?

While rare, it’s possible to contract norovirus twice quickly (within a week, two weeks, or a month). As previously explained, immunity to norovirus is multifactorial (virus mutations, antibodies, gene differences). Therefore, you can contract norovirus more than once in shorter periods, especially with re-exposure and in people with medical conditions affecting immunity (source 1) (source 2).

No one is completely immune to contracting norovirus more than once. However, certain factors and risk groups are more susceptible to such conditions:

• Older age.
• Not adhering to standard hygiene practices, especially during outbreaks.
• Compromised immunity is seen in leukemia, lymphoma, and organ transplant recipients (receiving immunosuppressives) (source).

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To understand why you can contract norovirus more than once, read the comprehensive explanation below.

Why can you get norovirus twice? (full explanation).

1- Our Immunity to Norovirus is Incomplete and Develops Slowly

We’re still trying to understand how immunity against norovirus works fully. Research has shown that specific antibodies play a role in protection against norovirus, and non-specific (innate) immunity also plays a crucial role.

Innate (non-specific) immunity includes:

• Phagocytes: immune cells that engulf cells infected with the virus.
• Natural killer cells (NK cells) & many other cells.
• The epithelial lining of the intestine acts as a barrier against the virus.
• Stomach acid barrier: HCL inside your stomach is a very effective germ and virus killer. Any decrease in your stomach acid by disease or a drug can increase your chance of contracting norovirus again.

Adaptive or specific immunity (AKA antibodies):

Antibodies against norovirus don’t offer complete protection against contracting norovirus more than once.

Also, a single infection with a specific strain of norovirus may not be sufficient for your immune system to produce enough antibodies. You may need more than one Infection with the same specific strain to develop immunity (source).

Researchers have found that some people without serum antibodies appear to be more protected than those with serum antibodies (source).

Also, immunity develops slowly, and antibodies against norovirus are estimated to last between 8 weeks to 6 months (source) (source).

The takeaway is that even antibodies may not provide protection, and you can contract norovirus more than once.

2- Norovirus Has Many Strains

Another factor contributing to reinfection with norovirus is the virus’s ability to mutate.

We know of at least seven sub-groups of norovirus. Multiple genotypes and mutations are recognized within each group. Genogroups GI, GII, and GIV are infectious to humans (source).

Antibodies against a specific strain don’t protect you from contracting norovirus for the second time by a different strain. This can theoretically occur after short periods within a week or a month.

All you need is to be exposed to the second norovirus strain again, especially if you don’t follow protective measures.

3- Norovirus is Very Stable, Resistant, and Extremely Contagious

In addition to being deceptive to your immunity, norovirus is also very resilient. Here are some interesting facts explaining why you can contract norovirus twice or more:

• Extremely contagious: A very small number of viruses can infect you (less than 100 viral particles (source); other studies suggest that it is as low as 18 viral particles (source).
• Stable: An infected person continues to infect others for about a month (source).
• Can be airborne: Norovirus infection can occur via airborne droplets of vomitus, fomite contamination, or food and water consumption.
• Resistant: Norovirus is resistant to ethyl alcohol. Therefore, hand hygiene with soap and water is better than alcohol. Also, standard cleaning agents don’t eliminate the virus; you can get infected twice (source).
• Norovirus mutations: the mutation of norovirus plays a significant role in reinfection. Norovirus is known for its genetic diversity and rapid evolution, largely due to mutations and recombination. This leads to the emergence of new strains over time (source).

All the above factors can cause Infection with norovirus more than once.

4- Your Genes Play a Role in Contracting Norovirus More Than Once

Certain blood groups and genetic factors may play a role in contracting norovirus more than once, even in a short period like a week or month. For example, the norovirus genogroup GI may bind preferentially to blood group A and O patients. Genogroup GII may bind to blood groups A and B patients (source).

5- Asymptomatic Persons are Common, Causing Infection

Many people can become infectious to others while asymptomatic. In this interesting study, researchers found that 12% of children under five years shed norovirus while having no symptoms.

Who is at a Higher Risk of Contracting Norovirus More Than Once?

• People who don’t follow the recommended hygienic methods.
• Older individuals, who have a weaker immune response to the virus.
• Any conditions affecting your immunity, such as leukemia, HIV, cancer chemotherapy, and autoimmune diseases.
• Exposure to higher doses of the viral particles.

How to Protect Yourself from Contracting Norovirus for a Second Time?

• Don’t Use Ethyl-Alcohol for Disinfection: it cannot kill norovirus.
• Wash your hands with soap and water instead.
• Use bleach (5 to 25 tablespoons of household bleach per gallon of water) to disinfect surfaces (instead of standard cleaning agents).
• Don’t prepare food for others if you have had a norovirus infection in the past month.

For more information on how to protect yourself from contracting norovirus twice, watch the video below from the CDC or refer to CDC information.

FAQs about norovirus reinfection:

Is there a vaccine for norovirus that can protect from reinfection?

Several potential vaccines are undergoing trials and showing initial positive results, but they haven’t been released for public use. The rapid mutation and the existence of numerous strains of norovirus pose a significant challenge in creating a universally effective vaccine.

Can norovirus infection become chronic?

Typically, a norovirus infection is acute, meaning it appears suddenly and lasts briefly. Most individuals recover within several days. However, in certain cases, especially in those with compromised immune systems, the virus can cause symptoms to persist for longer, potentially leading to a more severe illness. While the symptoms may last longer in these instances, it’s not usually classified as a “chronic” infection like some other viral infections.

For how long norovirus is contagious?

Norovirus is highly infectious and can be transmitted to others from the onset of symptoms until at least three days after recovery. Some individuals may remain infectious for up to two weeks post-recovery. This is why maintaining good hygiene, such as frequent and thorough handwashing, is crucial in preventing the virus’s spread.

What are my chances of getting a norovirus twice?