Q: Is a persistent fever, headache, and lethargy two weeks after Influenza A an aftereffect?

Medically reviewed by Sang Hyun Ahn, MD

Content edited by Myeongchan Kim, MD

This post is a dramatization of a question and answer session experienced by our actual medical reviewers. Please note that this content is for informational purposes only and does not constitute medical advice. Always consult with a qualified healthcare professional for any health concerns or before making any decisions related to your health or treatment.

Question:

My child had Influenza A two weeks ago, but they still have a persistent fever and are complaining of headaches. They have a slight cough and a runny nose. They have been taking prescribed medicine and Tylenol three times a day to manage the fever, and this two-week prescription is almost finished. Do I need to get another prescription? My child has been on medications for almost two months now.

Most importantly, the headaches started after a 5-day course of Tamiflu. My child just wants to sleep and seems very lethargic. Is this normal? Are these aftereffects of the flu? We are just trying to endure it with the prescription that includes Tylenol.

Answer:

It must be very worrying to see your child's fever and headache continue for over two weeks.

An immediate visit to the pediatrician today is strongly recommended.

You should have your child evaluated today if any of the following apply:

• The fever has lasted for more than 2 weeks after finishing Tamiflu.

• They have a headache, seem extremely lethargic, and only want to sleep.

• The fever does not drop after taking a fever reducer, or it spikes again immediately.

• They experience neck stiffness, repeated vomiting, or severe headaches.

Possible Causes:

• Secondary bacterial infection following Influenza A (such as sinusitis, an ear infection, or pneumonia).

• A concurrent infection with a different virus.

• Rarely, complications from the flu (such as encephalitis).

Even if the headache started at the same time as the Tamiflu treatment, a fever and severe lethargy persisting for two weeks cannot be explained solely by medication side effects.

Information to share with your doctor during the visit:

• The date of the flu diagnosis and the duration of Tamiflu treatment (5 days).

• The total number of days the fever has lasted.

• When the headache started and its characteristics (e.g., is it the whole head? one side? does it get worse with movement?).

• How often Tylenol is being taken and how long its effects last.

• Any new symptoms besides the cough and runny nose (e.g., ear pain, yellow mucus, neck stiffness, vomiting).

The doctor will likely perform a physical exam (listening to the chest, checking the ears and throat, and checking for neck stiffness) and may order blood tests, a chest X-ray, or a sinus evaluation to see if antibiotics need to be added or adjusted.

🚨 Go to the Emergency Room IMMEDIATELY if you notice any of the following:

• Difficulty or pain when bending the neck forward (stiff neck).

• Repeated vomiting accompanied by a severe headache.

• Blurred consciousness or extreme difficulty waking the child up.

• Difficulty breathing or bluish lips.

Precautions regarding medication:

• Tylenol (acetaminophen) should be given a maximum of 5 times a day (at 4 to 6-hour intervals).

• If your child has been taking medicine for two months, finding the underlying cause and treating it is the top priority.

• Fever reducers only temporarily relieve symptoms; they do not cure the underlying illness.

Summary:

A fever, headache, and lethargy lasting more than 2 weeks after the flu strongly point to a possible secondary infection or complication. Please visit your pediatrician today for a proper medical evaluation to determine the exact cause.

For extra peace of mind and clear guidance when tracking your child's symptoms, the FeverCoach app is always there to help.

fevercoach.us

Apple App Store

Google Play

🌐 Also available in: Español · 한국어