For a Texas nurse, the first sign that something was wrong happened while brushing her teeth — she couldn’t taste her toothpaste. For a Georgia attorney, it was hitting a wall of fatigue on a normally easy run. When a Wisconsin professor fell ill in June, he thought a bad meal had upset his stomach.

But eventually, all of these people discovered that their manifold symptoms were all signs of Covid-19. Some of the common symptoms — a dry cough, a headache — can start so mildly they are at first mistaken for allergies or a cold. In other cases, the symptoms are so unusual — strange leg pain, a rash or dizziness — that patients and even their doctors don’t think Covid-19 could be the culprit.