In some parts of the United States, health workers hand people the swab to test themselves, assuring a level of personal comfort. To many South Africans, the only Covid-19 test is a painful one — you see stars or gag because a nasal swab goes down your throat.

The range of swabbing raises questions: Who is doing it right? How deeply should the swab slide into your nostril? How long should it spend up there? Does an accurate test have to be uncomfortable? Unfairly or not, some countries have reputations for brutal tests.

First, a brief anatomy lesson: No, the swab is not actually stabbing your brain.