Can You Get Norovirus Twice? And When? A Complete Answer.

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?

Yes.

Center For Disease Control And Prevention states that you can get norovirus infection several times during a lifetime. Even if you have antibodies to norovirus, you are not protected from infection unless you get infected with the same norovirus strain more than once (ref).

Several risk factors are linked to getting norovirus twice such as (ref)

• Being older in age.
• Having chronic illnesses affecting your immunity, or
• Re-exposure to higher infective doses of the virus.

Norovirus became the most common viral cause of gastroenteritis in adults and children since the introduction of rotavirus vaccination.

Unlike rotavirus, there is no vaccine for norovirus. And the immunity for a virus is complex, incomplete, and not fully understood.

According to the CDC, You can get norovirus twice either by infection with another different strain. Also, you can get norovirus twice with the same strain (ref).

Several factors play a role in getting norovirus more than once. Besides the viral factors, the immunity to the norovirus is complex and not complete.

How fast can you get norovirus twice?

As we explained before, getting norovirus gastroenteritis doesn’t mean you will be immune. It is possible to get norovirus for the second time later 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 most common cause of diarrhea outbreaks. Outbreaks commonly occur between November and April. And you can get norovirus twice in the same season.

Although some people can develop immunity and have antibodies against norovirus, there is no guarantee to get reinfected.

This immunity is not complete and you need to be infected more than once to develop immunity to the specific strain of norovirus.

Also, the CDC states that antibodies are not the only immunological factor that fights norovirus. Another type of immunity “the innate immune response” and genetic differences may play a role.

The exact duration of immunity against norovirus is still unknown. And this may explain why so many people of all ages get norovirus during outbreaks (ref).

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

It is rare, but possible to get norovirus twice in a row (within a week or a month). As we explained before, immunity to norovirus is multifactorial (virus mutations, antibodies, gene differences). So you can get norovirus more than once in shorter periods especially with re-exposure and in people with medical conditions affecting immunity. (ref 1) (ref 2).

No one is immune against getting norovirus more than once, however, some factors and risk groups are more exposed to such conditions:

• Older age.
• Not following the standard hygienic methods especially during outbreaks.
• Disordered immunity as with leukemia, lymphoma, people with organ transplants (receiving immunosuppressives) (ref).

Image source

To know why you can get norovirus more than once, read the full explanation below.

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

1- Our immunity to norovirus is incomplete, develops slowly.

We currently don’t understand how exactly the immunity against norovirus works. Research has found that not only specific antibodies play a role in protection against norovirus, but also, non-specific (innate) immunity plays an important 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 present 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 getting norovirus twice.

Adaptive or specific immunity (AKA antibodies):

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

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

More interestingly, researchers have found that some people without serum antibodies appear to be more protected than people with serum antibodies. (ref).

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

The lesson we learned here, Even the presence of antibodies may not be protected and you can get norovirus more than once.

2- Norovirus has many strains.

Another factor contributing to reinfection with norovirus more than once is that norovirus is virtual mutations.

We know at least 7 sub-groups of norovirus. Multiple genotypes and mutations are recognized within each group. Genogroups GI, GII, and GIV are infectious to humans. (ref).

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

All you need is to get exposed again to the second norovirus strain. Especially if you don’t follow protective measurements.

3- Norovirus is very stable, resistant, and extremely contagious.

Besides being deceptive to your immunity, the norovirus is very strong. And here are some interesting facts explaining why you can get norovirus twice or more:

• Extremely contagious: A very small number of viruses can infect you (less than 100 viral particles (ref), other studies suggest that it is as low as 18 viral particles (ref).
• Stable: An infected person continues to be infectious to others for about a month. (ref)
• Can be airborne: Norovirus infection can occur via airborne droplets of vomitus, fomite contamination, or consumption of food and water.
• Resistant: norovirus resistant to alcoholo Therefore hand hygiene with soap and water is better than alcoholo. Also, standard cleaning agents don’t eliminate the virus and you can get infected twice (ref).

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

3- Your genes play a role in getting norovirus twice.

Certain blood groups and genetic factors may play a role in getting norovirus twice 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 (ref).

4- 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 5 years shed norovirus while having no symptoms.

Who is at a higher risk of getting norovirus twice?

• People who don’t follow the recommended hygienic methods.
• Older ages, 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 getting norovirus for a second time?

• Don’t Use Alcohol for disinfection: alcohol 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 norovirus infection in the past month.

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