Q: My child has a high fever, but the flu test was negative. The fever returned after an IV. What should I do?

Question:

My child started getting a fever yesterday. We went to the hospital this morning for a flu test, and the result was negative. However, the fever spiked to nearly 40°C (104°F) this afternoon. After receiving an IV drip, the fever went down, but now it's back up to 38.2°C (100.8°F). Since the flu test was negative the day after the fever started, can I be sure it's not the flu? This is my child's first time with such a high fever, and I'm very worried.

Answer:

It must be very alarming to see such a high fever for the first time. You're not alone in feeling this way. Many parents share your concerns.

Summary of the Current Situation

• Fever started yesterday at lunchtime.

• Negative flu test this morning.

• Fever reached nearly 40°C (104°F) at noon.

• Fever subsided after an IV drip (did it contain a fever reducer?) and is now 38.2°C (100.8°F).

  
  

Understanding Flu Test Timing

A rapid flu test can show a false negative if done too early (within 12 hours of symptom onset) or too late. Since the fever started yesterday at lunch and the test was done this morning (about 18-20 hours later), the timing was appropriate. A negative result means the flu is less likely, but it cannot be ruled out 100%. Other viruses, such as adenovirus or enterovirus, can also cause high fevers.

Check the IV Drip Components

Please confirm if the IV drip your child received at the hospital contained a fever reducer (like an acetaminophen injection). If it did, the current 38.2°C (100.8°F) fever could be the result of the medication wearing off. You can give another dose of an at-home fever reducer, making sure to follow the proper dosing interval.

What to Do at Home Now

• If you provide your child's age and weight, along with the name and concentration (mg/mL) of the fever reducer you have at home, I can guide you on the correct dosage.

• Offer small, frequent sips of lukewarm water (a few sips every 5-10 minutes).

• Dress your child in a single, thin layer of clothing and keep the room cool.

• Do not use wet towels or give a lukewarm bath, as this can cause shivering.

  
  

When to See a Doctor Again Today

• Your child seems to have difficulty breathing or has bluish lips.

• No urination for more than 8 hours.

• Excessively sleepy and difficult to wake, or shows a weak response when roused.

• Has a stiff neck, severe headache, or repeated vomiting.

• The fever does not respond at all to fever reducers or lasts for more than 3 days.

  
  

Points for Reassurance

More important than the high temperature itself is how your child behaves when the fever is down. Are they playing, drinking fluids, and urinating? The fever returning after the IV drip is likely because the medication wore off. Confirm the proper dose and interval for your at-home fever reducer, administer it, and continue to monitor your child's condition.

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