Summarize the following:
With a common cold, your fever should go away quickly. However, a lingering fever can be a sign that your infection is worsening. Your doctor can find out why your fever is getting worse and prescribe a treatment that can help.  For children under the age of 12, see a doctor if their fever lasts longer than 2 days. Babies under the age of 12 weeks need medical care for a fever of 100.4 °F (38.0 °C) or greater. A common cold typically starts to improve within a week. If your symptoms don’t seem to be going away, then your infection could be worsening, or you may have a different respiratory infection. It’s best to see your doctor to make sure you’re getting the proper treatment. You might experience the following symptoms:  Fever Severe sore throat Persistent cough, either dry or with phlegm Headache Sinus pain Severe body aches and pains Runny nose Sneezing Shortness of breath or wheezing The common cold shares symptoms with other respiratory infections, including the flu. If your symptoms are severe or don’t go away after a week, then your doctor might want to make sure you don’t have a more severe infection. They might want to do diagnostic tests, like the following:  Complete blood count (CBC) to look for an infection Chest X-rays to check your lungs for congestion or pneumonia Rapid flu test using a nasal or throat swab

Summary:
Visit your doctor for a fever above 101.3 °F (38.5 °C) or lasting 5 days. Seek care for symptoms that are severe or don't improve in 7 days. Undergo diagnostic tests to rule out other illnesses, if necessary.