I had it as an adult 10 years ago. I was in bad shape. The problem is that it grips you for 3months. A whole season of sickness. It wasn't so bad that I took time to deeply rest. It wore me thin, but it finally passed. Do all of the same things you would do for any cold (rest, fluids, nutrient dense foods), but keep doing them for what may seem like eternity. If its gone in less than 3months, thats a speedy recovery. Also, fresh air is supposed to be particularly healing. I went for long walks that winter, but I would get very tired and need to lay down. I would even fall asleep sitting on a rock and wake up as I was falling off. It wakes you up in the night. The cough launched my body up from deep sleep. So, you don't get a good night's sleep for 3 months either.
Your daughter will have life time immunity.
