Cassidy McCarthy, 27, was exhausted no matter how many hours she slept. “I felt like a zombie most days,” she says; her muscles ached, and she sometimes forgot words during conversations. McCarthy was awaiting the results from a battery of blood tests when intense chest pain sent her to the ER. Could it be a lingering viral infection? An anxiety attack? Her diagnosis came a week later: Lyme disease. “I had an uneasy feeling that my body hadn’t been in the best health for two years,” she says. “But with such a wide range of symptoms, I didn’t put it together.” She’s one of more than 300,000 people in the United States each year who are diagnosed with Lyme disease—almost 52 percent of them women. And like McCarthy, many victims suffer silently, since Lyme, and its symptoms, can be so difficult to decipher. This is what we know now.

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