How do i tell the difference between thrush and a symptom of measles

Measles=very sick: Patients with measles are very ill, with fever, lethargy and a rash which starts behind the ears and progresses down the body.There may be a few white dots inside the mouth. Thrush is a minor illness with white patches on the insides of the cheeks or on the tongue and lips, usually without fever or other signs of systemic illness.

No comparison: Thrush is a yeast infection in the baby's mouth and shows up as white, cheesy like material on the tongue, gums and sides of the mouth that doesn't scrape off like milk remnants. Measles is a rash all over the body and koplik spots are red spot on the inside of the cheeks.