~ Not everyone gets the flu when exposed to it.
~ Genetic variants can decrease your susceptibility to specific strains.
The dreaded influenza…
Have you ever wondered why some people never seem to get the flu when it is going around? Turns out that our genes play a role in both our immune response to the flu virus and the virus’s ability to replicate in us.
No one wants to get the flu. You feel terrible for a week or so, and the fatigue sometimes lingers even longer.
But have you ever noticed that some people never seem to get the flu?
It turns out that genetically, some people are protected against different variants of the influenza viruses.
Influenza – the flu – can be caused by several different strains of the virus. Usually, there is an influenza A (H3N2 or H1N1) and a strain of influenza B that circulates each year. The specific strains change each year.[ref]
Interestingly, studies show that the majority of people exposed to a new flu strain don’t get the flu – they remain asymptomatic.[ref]
The flu virus invades the epithelial cells that line your upper respiratory tract – nose, sinuses, pharynx, and larynx. Once the virus enters the cell, it is replicated by the host cell (your) RNA replication mechanisms. The new viral proteins reassemble and then are taken to the cell surface to be released.[ref]
Your immune system kicks into high gear to fight off the foreign viral proteins.
Immune system players:
Genetic variants in the cytokine-producing interleukin genes have been found to alter people’s susceptibility to the flu.
When the immune system recognizes the foreign viral particles through pattern recognition receptors, it activates production of pro-inflammatory cytokines and chemokines, including IL-1β (interleukin 1 beta).
These variants don’t completely protect you from getting the flu -just statistically make it less likely that you will come down with it. You still need to take the usual precautions against the flu… complications from the flu kill a lot of people each year.[ref]
A 2016 study looked at genetic variants in some of the genes involved in an immune response. It found that variants in IL17 (interleukin-17), IL28 (interleukin-28), and IL1B (interleukin-1 Beta) decreased the risk of getting the flu.[ref]
Keep in mind that even if you are at half the normal risk, you can still get the flu if you are exposed to it, especially if you have a compromised immune system.
Another part of your innate immune response is the complement system. The complement system proteins circulate in an inactive state and are triggered by certain microbes. Activation of this system then stimulates other parts of the immune system to kick into high gear.
Certain genetic variants in the complement system are linked to susceptibility to H1N1 flu strains.[ref]
Flu Genotype Report
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Genetic variants affecting susceptibility to H3N2 strains:
IL17 gene: encodes interleukin 17
Check your genetic data for rs2275913 (23andMe v4, v5)
- G/G: typical risk for H3N2 flu (compared to A/A)
- A/G: typical risk for H3N2 flu (compared to A/A)
- A/A: ~ half the risk for H3N2 flu[ref]
Members: Your genotype for rs2275913 is —.
IL1B gene: encodes interleukin 1B
Check your genetic data for rs16944 (23andMe v4, v5):
- A/A: typical risk for H3N2 flu
- A/G: typical risk for H3N2 flu
- G/G: less than half the risk for H3N2 flu[ref]
Members: Your genotype for rs16944 is —.
IL28 gene: encodes interleukin 28
Check your genetic data for rs8099917 (23andMe v4, v5):
- T/T: typical risk for H3N2 flu
- G/T: ~ half the risk for H3N2 flu
- G/G: ~ half the risk for H3N2 flu[ref]
Members: Your genotype for rs8099917 is —.
Genetic variants impacting H1N1 susceptibility:
The CCR5 gene codes for a protein on the surface of white blood cells. CCR5 is a chemokine receptor involved in our immune response. People who carry the CCR5delta32 variant are more resistant to HIV infection.
The CCR5delta32 variant has also been investigated in H1N1 flu cases. Several studies have found a link to susceptibility and increased severity of flu symptoms for people who carry the variant.[ref][ref] But not all studies agree.[ref]
Check your genetic data for i3003626 (23andMe v4,v5 [also known as rs333 and CCR5delta32]):
- II: typical
- ID: possibly higher risk of flu or increased severity of flu[ref][ref]
- DD: resistance to the common strains of HIV
Members: Your genotype for i3003626 is —.
The CD55 gene codes for the complement decay-accelerating factor, which regulates the complement system on immune cells. A variant of CD55 has been associated with the severity of H1N1 infection.[ref]
Check your genetic data for rs2564978 (23andMe v4):
- C/C: typical severity of flu
- C/T: typical severity of flu
- T/T: increased severity of H1N1 flu infection[ref]
Members: Your genotype for rs2564978 is —.
MBL2 gene: codes for mannose-binding lectin, which activates the complement system.
Check your genetic data for rs1800450 (23andMe v4, v5; AncestryDNA):
- C/C: typical
- C/T: likely to have lower mannose-binding lectin protein complex levels[ref], less likely to have severe H1N1[ref]
- T/T: mannose-binding protein deficiency[ref], greater risk of staph, MRSA, tuberculosis[ref][ref][ref], less likely to have severe H1N1[ref]
Members: Your genotype for rs1800450 is —.
FCGR2A gene: encodes a part of IgG
Check your genetic data for rs1801274 (23andMe v4, v5; AncestryDNA):
- A/A: 2x relative risk of severe pneumonia in H1N1 flu[ref]
- A/G: increased relative risk of severe pneumonia in H1N1 flu
- G/G: typical risk
Members: Your genotype for rs1801274 is —.
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Debbie Moon is the founder of Genetic Lifehacks. Fascinated by the connections between genes, diet, and health, her goal is to help you understand how to apply genetics to your diet and lifestyle decisions. Debbie has a BS in engineering and also an MSc in biological sciences from Clemson University. Debbie combines an engineering mindset with a biological systems approach to help you understand how genetic differences impact your optimal health.