Most people recover from flu B within about a week, though a lingering cough and fatigue can stick around for two weeks or longer. The acute phase, with fever, body aches, and chills, typically lasts five to seven days in otherwise healthy adults. How quickly you bounce back depends more on your overall health, age, and how early you start treatment than on whether you have flu A or flu B specifically.
Day-by-Day Recovery Timeline
Flu B symptoms usually appear one to four days after you’re exposed to the virus. The first two to three days tend to be the worst, with high fever, intense body aches, headache, sore throat, and exhaustion hitting all at once. Fever and the most severe symptoms generally start improving around day four or five.
By the end of the first week, most adults feel noticeably better. But “better” doesn’t mean “back to normal.” Even after the fever breaks and the worst symptoms resolve, you can expect to feel run down for another one to two weeks. A dry, nagging cough and general fatigue are the most common holdovers. In older adults especially, that cough and low energy can persist well beyond two weeks.
Recovery in Children
Kids tend to get through the acute illness in less than a week, similar to adults. The difference is in how long the fatigue drags on: children can feel tired and low-energy for three to four weeks after the fever is gone. Young children and those with underlying conditions like asthma face a higher risk of complications, including ear infections and pneumonia. Flu can also trigger asthma flare-ups that extend recovery further.
When You’re Still Contagious
You can spread flu B starting the day before your symptoms appear, which is part of why it moves through households and classrooms so efficiently. Adults remain contagious for roughly five to seven days after symptoms begin, with the highest risk of spreading the virus during the first three to four days of illness, particularly while you still have a fever. Children, people with weakened immune systems, and those who are severely ill can shed the virus for 10 days or more.
The CDC recommends staying home until at least 24 hours have passed where both of these are true: your symptoms are improving overall, and you haven’t had a fever without using fever-reducing medication. That’s the minimum. If you’re still coughing frequently or feeling weak, you may want to give it a few extra days before returning to work or school.
How Antivirals Affect Recovery Time
Prescription antiviral medications can shorten flu B by roughly a day, but only if you start them within the first 48 hours of symptoms. For flu B specifically, one newer antiviral reduced symptom duration by more than 24 hours compared to the older, more commonly prescribed option. Your doctor is most likely to recommend antivirals if you’re at higher risk for complications: young children, adults over 65, pregnant women, or people with chronic health conditions.
If you’re past that 48-hour window, antivirals are less likely to make a meaningful difference in how long you’re sick. At that point, recovery is mostly about rest, fluids, and managing symptoms with over-the-counter fever reducers and pain relievers.
Flu A vs. Flu B Recovery
There’s no significant difference in how long flu A and flu B last. Both typically resolve within about a week, and both can leave you with a trailing cough and fatigue. The variation in recovery time has much more to do with your individual health, age, and immune response than with which strain you caught.
Lingering Cough After Flu B
A post-viral cough is one of the most common complaints after the flu, and it can last three to eight weeks. This happens because the virus inflames and irritates your airways, and that irritation takes time to heal even after your body has cleared the infection. The cough is usually dry and unproductive, worse at night, and not a sign that you’re still sick or contagious.
If your cough persists beyond a couple of weeks after your other symptoms have cleared, or if it gets worse instead of gradually improving, that’s worth a conversation with your doctor to rule out a secondary infection like bacterial pneumonia.
What Slows Recovery Down
Several factors can push your recovery well past the one-week mark:
- Age: Older adults and young children tend to have longer recovery periods, particularly when it comes to fatigue and cough.
- Chronic conditions: Asthma, diabetes, heart disease, and weakened immune systems all increase the risk of complications that extend illness.
- Pushing it too soon: Returning to full activity before your body is ready can set you back. The fatigue after flu is real, not just being “a little tired,” and ignoring it often prolongs recovery.
- Dehydration: Fever and reduced appetite during the flu make dehydration common, which worsens fatigue and slows healing.
The bottom line: plan for about a week of feeling genuinely sick, followed by one to two weeks of gradually getting back to full strength. If you’re still worsening after the first week, developing new symptoms like chest pain or difficulty breathing, or running a fever that returns after it had gone away, those are signs of a possible complication that needs medical attention.