Can you get the same virus twice?

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It depends entirely on which virus, and the spectrum runs from "once, ever" to "every winter." The one-and-done group: measles, mumps, rubella, and chickenpox typically give durable lifelong immunity after infection (or vaccination), which is why getting measles twice is genuinely rare. The repeat-offender group works through two tricks. Trick one is mutation: influenza and SARS-CoV-2 change their surface proteins constantly, so last year's immunity only partially recognizes this year's strain, which is exactly why flu shots update annually. Trick two is fading or narrow immunity: common-cold coronaviruses and RSV produce immunity that wanes within months to a year or two, and norovirus immunity is both short-lived and strain-specific, so you can catch a different norovirus strain immediately after recovering from the last one. A few viruses do both tricks at once. Then there is the sleeper category: herpesviruses (cold sores, chickenpox, mono's EBV) never leave; they go dormant in your nerves or cells and can reactivate later, which is not a new infection but the old one waking up, as shingles painfully demonstrates. The practical implications: vaccination remains worth it even after infection (it broadens and strengthens the response), a "repeat" flu is usually a new strain rather than the old one returning, and persistent post-viral fatigue is more often immune aftermath than reinfection.

Can you get the same virus twice?

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