Quick answer: Flu symptoms usually start suddenly 1 to 4 days after exposure, most often around day 2. Fever, chills, body aches and exhaustion are worst in the first 3 days and usually improve by days 5 to 7, but cough and tiredness can last 2 weeks or more. You are most contagious in the first 3 to 4 days. Getting tested in the first 48 hours gives antiviral treatment the best chance to help.
The flu doesn’t creep in like a cold. Most people say it feels like being hit by a truck. Knowing what to expect each day helps you decide when to rest at home and when to get seen.
Common flu symptoms
- Sudden fever of 100°F or higher, or feeling feverish with chills (not everyone with flu has a fever)
- Body and muscle aches
- Extreme tiredness
- Dry cough
- Sore throat
- Headache
- Runny or stuffy nose
- Vomiting or diarrhea, more common in children
Not sure it’s flu? Compare cold, flu and COVID symptoms. Vomiting and diarrhea without fever and aches may be a “stomach flu,” which is a different illness (see food poisoning vs. stomach flu).
Flu timeline: day by day
| Day | What it usually feels like | What to do |
|---|---|---|
| Exposure to day 1 | No symptoms, but you may already be contagious the day before you feel sick | Wash hands, avoid close contact if someone at home is sick |
| Days 1 to 3 | Sudden fever, chills, aches, headache, exhaustion. This is usually the worst stretch | Get a rapid flu test. Antivirals work best within 48 hours |
| Days 4 to 5 | Fever starts to break; cough, sore throat and congestion may stand out more | Rest, fluids, watch for warning signs |
| Days 6 to 7 | Most people feel noticeably better | Return to normal activities once fever-free 24 hours without medicine and improving (see how long to stay home) |
| Week 2 and beyond | Lingering cough and fatigue are common | Get checked if you get worse again, which can signal a complication |
How long is the flu contagious?
Most adults can spread the flu from about 1 day before symptoms start until 5 to 7 days after. You’re most contagious in the first 3 to 4 days. Young children and people with weakened immune systems can spread it longer.
When to get seen
- You’re in your first 48 hours and at higher risk (65+, pregnant, chronic conditions)
- Your child is under 5 or has asthma (see flu in kids)
- Your fever lasts more than 3 days or you can’t keep fluids down
- You start to feel better, then get worse again with fever and a worse cough
Learn about treatment options in Tamiflu and the 48-hour window, or start with a flu telehealth visit if you’d rather not leave home.
Go to the ER or call 911 for
- Trouble breathing or shortness of breath
- Chest pain or pressure
- Confusion, dizziness or being hard to wake
- Seizures
- Not urinating, or other signs of severe dehydration
- Bluish lips or face
Full list: flu warning signs: urgent care or ER?
Frequently asked questions
How long does the flu last?
Most people recover in 3 to 7 days, but cough and fatigue can last 2 weeks or longer.
What day of the flu is the worst?
Usually days 2 and 3, when fever and body aches peak.
Can you have the flu without a fever?
Yes. Some people, especially older adults, have flu without a fever. A flu test can confirm it.
When is the flu no longer contagious?
Most adults stop being contagious about 5 to 7 days after symptoms begin. Children may be contagious longer.
Where can I learn more?
See the CDC’s flu symptom guidance at cdc.gov/flu and this season’s trends in our Virginia flu season tracker.
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.
