A friendly, research-based guide for families, the general public, and healthcare readers.
- Common flu symptoms: fever/chills, cough, sore throat, runny/stuffy nose, body aches, headache, fatigue.
- Testing/antivirals work best within 48 hours.
- Flu A vs Flu B: symptoms overlap; Flu A can drive larger waves.
- Typical illness lasts ~3–7 days; cough/fatigue can linger.
- U.S. flu season usually Oct–May, peak Dec–Feb.
What the Flu Is—and Isn’t
Influenza is a contagious respiratory illness caused by influenza viruses, primarily types A and B. It’s different from a common cold and from “stomach flu.” Flu typically starts suddenly and feels more intense than a cold. For a quick overview of symptoms and complications, see the CDC’s symptom guide.
Early Flu Symptoms 2025 (What to Watch For)
- Fever or chills, cough, sore throat
- Runny/stuffy nose, headache
- Muscle/body aches, fatigue
- Occasionally vomiting/diarrhea (more common in children)
If testing confirms flu, antivirals can shorten illness and reduce complications—especially when started within 48 hours and for those at higher risk. Learn more from the CDC’s antiviral page.
Flu A vs Flu B
- Hosts & spread: Flu A infects humans and some animals and can drive larger seasonal waves; Flu B circulates mainly in humans.
- Symptoms: Overlap substantially; type can’t be reliably determined by symptoms alone.
- Severity: Either type can be severe in young children, older adults, pregnant people, and those with chronic conditions.
Background on virus types: CDC: Types A & B.
How Long Does the Flu Last?
- Acute phase: typically 3–7 days of fever and respiratory symptoms.
- Lingering: cough and fatigue may persist for 1–2+ weeks.
- Contagiousness: often from about 1 day before symptoms up to 5–7 days after onset (longer for children/immunocompromised).
Pneumonia Symptoms: When Flu Becomes More Serious
Watch for red flags that suggest pneumonia or other complications:
- Shortness of breath, rapid breathing, or chest pain
- Persistent high fever or a fever that returns after improving
- Worsening cough, confusion, severe weakness, dehydration
- Blue lips/face
More on pneumonia symptoms: CDC: Pneumonia.
“New Virus 2025”? Staying Current
Each season brings changing flu strains and other respiratory viruses. For timely U.S. updates (what’s rising, where, and how fast), follow official surveillance rather than headlines.
When Is Flu Season in the U.S.?
Flu activity typically runs from October through May and often peaks between December and February. Regional timing varies year to year. See the CDC’s season overview.
Flu Shot 2025: Who Needs It and When
- Who: Everyone 6 months and older (with rare exceptions).
- When: Ideally by end of October; later still helps.
- Why: Lowers risk of illness, hospitalization, and complications.
When to Seek Urgent Care or the ER
Emergency signs—call 911 or go to the ER:
- Trouble breathing, chest pain/pressure
- New confusion, difficult to wake
- Blue lips/face, seizures, fainting, severe dehydration
- In children: fast/labored breathing, ribs pulling in, inability to drink, no tears, fewer wet diapers, or sudden worsening
Need timely care (not an emergency)? Find nearby clinics with the U.S. federal locator: HRSA Health Center Finder.
At-Home Care & Prevention
- Rest and hydrate; consider acetaminophen or ibuprofen as directed for fever/aches.
- Stay home while feverish and for 24 hours after fever ends without medicine.
- Mask if you must be around others; improve indoor ventilation.
- Ask a clinician about antivirals if high-risk or within 48 hours of symptom start.
- Hand hygiene and routine surface cleaning help limit spread.
FAQs
Flu A vs Flu B—what’s the difference?
Both cause seasonal flu, and symptoms overlap. Flu A has broader animal reservoirs and can drive larger waves; Flu B circulates mainly in humans.
How long do flu symptoms last?
Acute symptoms usually resolve in 3–7 days; cough and fatigue may linger for a week or two longer.
When is flu season 2025?
Generally October–May in the U.S., often peaking December–February, with variability by region and year.
What pneumonia symptoms should prompt care?
Shortness of breath, chest pain, persistent high fever, confusion, or worsening cough warrant prompt evaluation.
Who should get the flu shot in 2025?
Everyone 6 months and older, ideally by the end of October.
Medical disclaimer: This guide is for general education and not a substitute for professional medical advice. In an emergency, call 911 (or local emergency services).