There are many synonyms that can be used instead of "quarantined." Some options include isolated, confined, separated, segregated, sequestered, and restricted. Each of these words has a slightly different connotation or usage, but all refer to a similar state of being in which someone or something is kept apart from others for health or safety reasons. While "quarantined" is the most common term used in the context of a pandemic or outbreak, it's always useful to have a range of synonyms at your disposal to help vary your language and add depth to your writing.