Influenza B: Symptoms, Treatment, and How It Differs From Flu A

Primary Symptoms

• Fever: Usually high (100.4°F or higher) and may last 3-5 days

• Body aches: Muscle pain throughout the body, especially in back and legs

• Dry cough: Often persistent and may worsen at night

• Fatigue: Extreme tiredness that can last for weeks

• Headache: Often severe and accompanied by sensitivity to light

• Sore throat: Scratchy or painful throat, especially when swallowing

• Runny or stuffy nose: Nasal congestion that may develop later in illness

When to Seek Care

Watch for signs of complications that need medical attention. These include difficulty breathing, chest pain, persistent high fever, severe headache, or confusion. Children may show different warning signs like rapid breathing, bluish skin color, or extreme irritability.

When to Seek Immediate Care

Contact a doctor right away if you notice any of the warning signs above, or persistent vomiting or signs of dehydration.

Conservative Treatments

• Rest and hydration: Get plenty of sleep and drink fluids to prevent dehydration

• Fever reducers: Over-the-counter medications like acetaminophen or ibuprofen

• Cough suppressants: Help reduce persistent dry cough, especially at night

• Throat lozenges: Soothe sore throat and reduce irritation

Advanced Treatments

• Antiviral medications: Four prescription antivirals treat influenza B: oseltamivir (Tamiflu), baloxavir (Xofluza), zanamivir (Relenza), and peramivir (Rapivab). They work best when started within 48 hours of symptoms. People at high risk of complications, and anyone in the hospital, should still be treated after 48 hours. Amantadine and rimantadine never work against influenza B.

• Inhaled medications: Bronchodilators may help people with asthma or other breathing problems whose symptoms flare during the flu. The inhaled antiviral zanamivir isn't recommended for people with asthma or chronic lung disease.

• IV fluids: For severe dehydration or inability to keep fluids down.

Medical History & Physical Examination

Your doctor will ask about your symptoms, when they started, and your recent activities. They'll check your temperature, listen to your lungs, and examine your throat and nose. The timing of your illness matters. Flu season typically runs from October through May, and influenza B can keep circulating into spring.

Diagnostic Testing

• Rapid influenza test: Quick test using a nasal swab, results in 15-20 minutes

• RT-PCR test: More accurate test that identifies specific flu strains

• Viral culture: Lab test that takes several days but provides detailed information

Daily Management Strategies

Stay home for at least 24 hours after your fever breaks to avoid spreading the virus. Use tissues when coughing or sneezing, and wash your hands frequently. Keep your living space well-ventilated and avoid close contact with family members when possible. If your symptoms worsen, read when to go to the hospital for the flu.

Exercise & Movement

Avoid strenuous exercise while you have fever or body aches. Light activities like gentle walking may help once you start feeling better. Gradually return to normal activity levels as your energy improves. Listen to your body and rest when needed.

Everyday Prevention Steps

• Get an annual flu vaccine: the 2026 to 2027 trivalent vaccine includes one B/Victoria strain; B/Yamagata is no longer included

• Wash your hands frequently with soap and water for at least 20 seconds

• Avoid touching your face, especially your nose, mouth, and eyes

• Stay away from sick people when possible during flu season

• Clean and disinfect frequently touched surfaces regularly

• Maintain a healthy lifestyle with good nutrition and adequate sleep