How Long Does Type B Flu Usually Last?

Although seasonal flu viruses are detected in the U.S. throughout the year, flu viruses typically circulate during the fall and winter, also known as the “flu season.”

Influenza viruses are divided into four main types:

• Type A
  • A(H1N1)
  • A(H3N2)
• Type B
  • B/Yamagata
  • B/Victoria
• Type C
• Type D

Influenza A and B cause seasonal epidemics of disease. Influenza A viruses are the only viruses known to cause pandemics (global epidemics). Influenza C viruses generally cause mild illness, whereas influenza D viruses primarily affect cattle and are not known to infect or cause illness in humans.

For most people, the flu is a short-term illness with symptoms that appear 1-4 days after exposure to the virus. Flu type B symptoms typically occur suddenly and may be mild to severe:

• Fever or chills
• Cough
• Sore throat
• Runny or stuffy nose
• Muscle/body aches
• Headache
• Fatigue
• Vomiting and diarrhea (commonly seen in children)

Experts believe that flu viruses are spread predominantly by tiny droplets expelled when someone with flu coughs, sneezes, or talks.

These droplets may reach the mouths or noses of people nearby (about 6 feet away). Less often, a person may get the flu by touching a contaminated surface or object and then touching their mouth, nose, or eyes.

Pregnant women, people older than 65 years, young children, and people with certain health conditions such as asthma, diabetes, or heart disease are at a higher risk of serious flu complications.

Flu viruses can be detected in infected people 1 day before symptoms begin and up to 5-7 days after getting sick.

The contagious period varies depending on age group and viral load:

• Adults with the flu are most contagious in the first 3-4 days of the illness.
• Healthy adults may be able to infect others one day before symptoms have developed and up to 5-7 days after symptom onset.
• People with weakened immune systems and children (younger than 5 years) may be contagious for longer.

Flu type B is generally diagnosed based on typical symptoms. 

Reverse transcription-polymerase chain reactions or viral culture of nasopharyngeal or throat secretions are the gold standards for determining influenza virus infection. Tests may be ordered as well, such as:

• Rapid influenza diagnostic tests: Detects the virus (antigens) that stimulates an immune response
• Rapid molecular assays: Detects the genetic material of the flu virus

The best way to reduce your risk of getting the flu and its potentially serious complications is by getting vaccinated each year. According to the CDC, the flu vaccine helps reduce flu-related illnesses and the risk of serious complications that can result in hospitalization or even death.

Seasonal flu vaccines do not protect against influenza C or D viruses or animal-origin (zoonotic) flu viruses, such as avian flu viruses, which can cause human infections.

Treatment options for flu type B include:

• Antiviral drugs
  • Antiviral drugs are prescription medications (pills, liquid, an inhaled powder, or an intravenous solution) that fight against flu viruses in the body.
  • FDA-approved antiviral drugs recommended by the CDC include:
    • Tamiflu (oseltamivir phosphate)
    • Relenza (zanamivir)
    • Rapivab (peramivir)
    • Xofluza (baloxavir marboxil)
  • The most common side effects of these antiviral drugs are nausea, vomiting, bronchospasm, and diarrhea.
• Pain relievers for fever and aches:
  • Tylenol (acetaminophen)
  • Advil, Motrin (ibuprofen)
  • Aleve (naproxen)
• Adequate rest
• Drinking plenty of fluids

Potential flu complications include:

• Bacterial pneumonia
• Ear infections
• Sinus infections
• Myocarditis (inflammation of the heart)
• Encephalitis (inflammation of the brain)
• Myositis or rhabdomyolysis (inflammation in the muscles)
• Respiratory or kidney failure
• Sepsis
• Worsening chronic conditions such as congestive heart failure, asthma, or diabetes

If you experience any of the following symptoms, seek immediate medical attention:

Adults

• Difficulty breathing 
• Pain or a feeling of pressure in the chest/abdomen
• Persistent dizziness or confusion
• Inability to awaken from sleep
• Seizures
• Difficulty urinating
• Severe muscle pain
• Severe weakness or unsteadiness
• Worsening fever or cough 
• Worsening symptoms of chronic medical conditions

Children

• Rapid or troubled breathing
• Bluish lips or face
• Chest pain
• Severe muscle pain 
• Dehydration (inability to pass urine for 7 hours, dry mouth, and decreased tear production)
• Decreased alertness
• Seizures
• Fever higher than 104 F
• Worsening fever or cough