A PCR test stands for Polymerase Chain Reaction test. It is a very quick and easy-to-perform test used to detect any diseases or conditions that might affect your ability to travel. Depending on the disease/condition, you may need a medical certificate from a doctor to travel. As the name suggests, PCR uses a special technique to replicate the DNA of the pathogen so that it can be identified. This test looks for the DNA in your blood sample and will determine if the pathogen is present.
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https://makelisting.com/health_blog/what-is-a-pcr-test-and-why-should-i-consider-taking-one-before-traveling-internationally/