How can two relatively healthy people with similar lifestyles, when both infected with a disease, have different reactions to the sickness?

Question

For that matter, how could one of them show no symptoms (asymptomatic), while the other could be floored for days?

In: 0

Answer 1

Your immune system is determined by your genetics more than your lifestyle. Even if two people live similar lifestyles, their immune systems could react very differently to the same threat (any given disease).

Remember, some people’s immune systems launch an all-out mega response to harmless things like peanuts – that’s what allergies are. Immune system over-reacting to something harmless. And the reason some people’s immune systems do that isn’t their lifestyle.*

*Yes under-exposure to germs as an infant predisposes you to worse allergies later, but that’s not the point and beyond ELI5. Me and a co-worker can have the exact same lifestyle for the last 10 years yet my peanut butter sandwich would kill him. People’s immune systems differ wildly due to genetics.