If along with other aforementioned symptoms, you are experiencing heart problems, ask your doctor about the possibility of hypothyroidism. (healthcentral.com)
Most recover from Yellow Fever in under a week, unless you're one of the unlucky 15 % who enter the toxic phase, which sees the aforementioned symptoms plus abdominal pain, vomiting (sometimes with blood) seizures, delirium, decreased urination, and bleeding from the nose, mouth, and eyes. (havebabywilltravel.com)
It can also be exacerbated by lack of food, water, and not sleeping well due to all the aforementioned symptoms. (babygaga.com)