Mystery #2Tier 2-3microbes / immunity
Why don't you usually catch the same illness (like chickenpox) twice?
Plenty of children get chickenpox once, itchy spots for a week or so, and then never get it again, even when a friend has it. Catching the very same illness a second time is unusual. How does your body 'remember' a germ it met years ago?
Your guess
What's your hunch about why having an illness once often stops you catching it again?
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