Signs of serious illness include:

• Severe neck stiffness or pain.
• Confusion or extreme irritability.
• Extreme sleepiness.
• Persistent nausea or vomiting.
• Fever.
• Yellow color to the skin or eyes (jaundice).
• Abnormal bleeding, such as unexpected vaginal bleeding, rectal bleeding, or blood in the urine.
• Severe sensitivity to light (photophobia).
• Unsteadiness or dizziness that prevents standing or walking (ataxia or vertigo).
• New double vision, blurred vision, or blind spots.
• Very fast or difficult breathing.
• Very fast, very slow, or irregular heart rate (arrhythmia).
• Profuse sweating (diaphoresis).
• Severe pain.
• New and different skin rash.
• An increase in the size and number of bruises.

When fatigue occurs along with other signs of a serious illness, a visit to a health professional is required.