Influenza B can be serious. It causes seasonal flu with fever, cough, body aches and may lead to pneumonia, dehydration, worsening of chronic illnesses, hospitalization, or rarely death. Risk is higher for young children, older adults, pregnant people and those with chronic conditions. Annual flu vaccination and early antiviral treatment reduce risk; seek medical care for trouble breathing, persistent high fever, confusion, or worsening symptoms.

Influenza B causes seasonal flu — an acute respiratory infection with sudden fever, cough, sore throat, runny or stuffy nose, body aches, headache, chills and fatigue. It can lead to complications such as viral or secondary bacterial pneumonia, bronchitis, sinus and ear infections, and worsening of chronic conditions (asthma, heart disease). Severe illness and hospitalization are more likely in young children, older adults, pregnant people, and immunocompromised individuals.

Being influenza B positive means a diagnostic test detected influenza B virus, indicating an active flu infection. You may have fever, cough, sore throat, body aches and fatigue, and you’re contagious—especially in the first few days. Most recover with rest, fluids and symptom relief; antivirals can help if started early. Stay home to limit spread and seek medical care if high-risk or symptoms worsen.

Yes. Influenza B is contagious and people should isolate at home while symptomatic and until at least 24 hours after fever subsides without fever-reducing medicines. Adults are infectious about one day before symptoms start and for about 5–7 days after; children and immunocompromised people may shed virus longer. Use masks, hand hygiene, respiratory etiquette, and seek medical advice about antivirals if high risk.

Influenza B cannot be “cured” by a single medicine, but it is usually self‑limiting. Antiviral drugs (e.g., oseltamivir or zanamivir) started within 48 hours can shorten illness and reduce complications. Care focuses on rest, fluids, fever control and monitoring. Seek prompt medical help for severe symptoms or if you’re high‑risk. Annual flu vaccination reduces the chance of infection.

Generally, COVID-19 is more severe than influenza B at a population level: it causes higher rates of hospitalization, complications, and deaths and carries a risk of long COVID. Influenza B can be serious—especially in children, the elderly, and people with chronic conditions—but outcomes depend on variant, prior immunity, and vaccination. Vaccination and early treatment reduce severity for both.