Quick answer: The most common flu complications are pneumonia, sinus infections, ear infections, and worsening of asthma, COPD, heart disease or diabetes. Less common but serious complications include inflammation of the heart, brain or muscles, and sepsis. A key warning sign is feeling better and then getting worse again with fever and a deeper cough. Get seen promptly if that happens.
Most people bounce back from the flu in about a week. But the flu can weaken your body’s defenses and open the door to other infections, or make an existing condition worse. Here’s what to watch for.
Common flu complications
Pneumonia
Pneumonia is the most serious common complication. It can be caused by the flu virus itself or by bacteria that take hold afterward. Watch for:
- A cough that gets worse instead of better, sometimes with colored mucus
- Fever that returns after breaking
- Shortness of breath or chest pain when breathing deeply
At PACS we can check with an exam and an on-site chest X-ray. Bacterial pneumonia may need antibiotics (see can urgent care prescribe antibiotics?). Severe shortness of breath needs the ER.
Sinus infections
Facial pain or pressure, thick nasal discharge and congestion lasting more than 10 days, or getting worse after a week, may point to a sinus infection. Read sinus infection or sore throat?
Ear infections
Especially common in young children after the flu. Signs include ear pain, tugging at the ear, fussiness and new fever. See ear infections and pink eye.
Asthma and COPD flare-ups
The flu inflames the airways and can trigger wheezing and breathing trouble. A nebulizer treatment can help. Read asthma flare-ups: can urgent care help?
Dehydration
Fever, poor appetite, vomiting and diarrhea can drain fluids, especially in kids and older adults. Signs include very dark urine, dizziness and dry mouth. Mild to moderate cases can be treated with IV fluids. See dehydration: when to get help.
Worsening chronic conditions
The flu can make diabetes harder to control and raises the risk of heart attack and stroke in the weeks after infection. People with these conditions are at higher risk and should be seen early.
Rare but serious complications
- Myocarditis (inflammation of the heart)
- Encephalitis (inflammation of the brain)
- Myositis (muscle inflammation, sometimes causing severe leg pain in kids)
- Sepsis
These need emergency care. See flu warning signs: urgent care or ER?
How to lower your risk
- Get a yearly flu shot
- Get seen early. Antivirals started within 48 hours lower the risk of complications
- Rest, stay hydrated and don’t return to activity too soon (see how long to stay home)
Frequently asked questions
How do I know if the flu turned into pneumonia?
Signs include a worsening cough, returning fever, shortness of breath and chest pain when breathing. A provider can check with an exam and chest X-ray.
Can the flu cause an ear infection?
Yes, especially in young children.
Why do I feel worse after a week of the flu?
Getting worse after improving can signal a secondary infection. Get seen right away. Compare with the normal course in flu symptoms day by day.
Where can I learn more?
See the CDC’s flu complications information at cdc.gov/flu.
Get care today at PACS Urgent Care
Walk in or book online at our Alexandria flu clinic (3481 N Beauregard St, open 7 days, 8 AM to 8 PM) or book at our Ruther Glen flu clinic (17067 Merchants Dr, Monday to Friday 8 AM to 8 PM, Saturday and Sunday 9 AM to 5 PM). Prefer to stay home? Start with a telemedicine visit.
This article is general information and is not a substitute for advice from your own clinician.
