• Younger than age 3 months and has a rectal temperature of 100.4 F (38 C) or higher.
• Between ages 3 and 6 months and has a rectal temperature up to 102 F (38.9 C) and seems unusually irritable, lethargic or uncomfortable or has a temperature higher than 102 F (38.9 C).
• Between ages 6 and 24 months and has a rectal temperature higher than 102 F (38.9 C) that lasts longer than one day but shows no other symptoms. If your child also has other signs and symptoms, such as a cold, cough or diarrhea, you might call your child's doctor sooner based on severity.

Вот рекомендации когда надо идти к врачу

Американцы считают, что вот это список случаев для детей до двух лет.

Плюс ещё вот такие кейсы

Call your child's doctor if your child:
• Is listless or irritable, vomits repeatedly, has a severe headache or stomachache, or has any other symptoms causing significant discomfort.
• Has a fever after being left in a hot car. Seek medical care immediately.
• Has a fever that lasts longer than three days.
• Appears listless and has poor eye contact with you.

Да