Flu Virus B: Causes, Treatment and Prevention

Flu virus B, or influenza B, is one of the two main types of influenza that cause the winter flu in Australia. It brings on a sudden high temperature, body pain and tiredness, much like type A, and it spreads only between people. Most healthy adults recover at home within a week or two, but it can be serious for some.

Key takeaways

• Influenza B causes the same kind of illness as type A and is often as unpleasant.
• Symptoms start suddenly, one to four days after catching it.
• Antivirals work best within 48 hours and suit people at higher risk.
• The yearly flu vaccine protects against both types.
• Call 000 for trouble breathing, chest pain or confusion.

Where Influenza A and B Come From

Influenza A circulates in birds and animals as well as people, which is why it can cause pandemics, while flu virus B spreads only from person to person. The table compares the two types.

Common Flu Symptoms With Influenza B

The common symptoms of influenza B are a sudden fever, muscle aches, a headache, a dry cough, a sore throat, a runny or blocked nose and deep tiredness. Flu virus B tends to hit hard over a few hours, which helps tell it apart from a cold that builds slowly. Children sometimes vomit or have diarrhoea too, and a child with influenza should see a GP in person.

Are the symptoms different for A and B? Not in any way you can feel, as both types cause the same symptoms, so only a swab can tell them apart. Most symptoms ease within a week, though fatigue can linger for weeks.

How Flu Virus B Infects the Airways

The virus can infect you through the nose, throat or eyes, then multiplies in the lining of the airways, causing the swelling, mucus and inflammation behind the respiratory symptoms. Your immune response brings the temperature and body pain. Is influenza A or B worse? In most seasons type A causes more hospital stays, but outbreaks of type B can be severe. Antiviral medications can shorten either if started early.

Severity of Influenza A Compared With B

Influenza A and influenza B are similar in severity for most healthy adults, though influenza A more often causes large outbreaks and serious illness in older people. Influenza B can still cause health complications such as pneumonia, a bacterial infection on top of the flu, sinus and ear infections, worsening asthma or heart disease and, rarely, inflammation of the heart or brain. Influenza B treatment and prevention are the same as for type A: rest, antivirals for those who need them, and the vaccine. The virus also lives for hours on surfaces, so it spreads easily at home and work.

Treatment for Flu Virus B

Treatment for most people is rest, plenty of water and paracetamol or ibuprofen for the temperature, pain and sore throat, following the packet directions. Antibiotics do not work on a respiratory virus. An antiviral medicine, which is only available on prescription in Australia, can shorten the illness if started within 48 hours, and suits people at higher risk. How long can a flu virus last? Usually a week, with some tiredness after.

Prevention With the Yearly Flu Vaccine

The yearly vaccine is the best protection, because it covers the main influenza A and B strains expected each flu season. It is best given in April or May, before the seasonal peak, and is free for people aged 65 and over, children from 6 months to under 5, pregnant people, Aboriginal and Torres Strait Islander people and those with some medical conditions. Washing your hands, covering a cough and staying home while sick also cut the spread.

When Influenza B Needs a Doctor

See a doctor early if you are over 65, pregnant, or live with a lung, heart, kidney or immune condition, as influenza B can be more serious for you and antivirals work best in the first 48 hours. Also see a doctor if your fever lasts more than three days, or you start to feel better and then get worse. Call 000 for trouble breathing, chest pain, confusion or blue lips. A Medio GP can assess you in a phone consult and, where the doctor thinks it right, send an eScript.

Summary

Flu virus B causes a sudden illness much like type A, and most adults recover with rest within a week or two. Antivirals help people at higher risk if started early, and the yearly vaccine is the best protection. If you are worried about flu virus B, a Medio GP can assess you by phone, advise on care at home and, where the doctor thinks it right, send an eScript or give a pathology request for a swab.

Frequently asked questions

Is the flu bad this year?

Each flu season is different, and your state health department publishes regular reports on how many cases there are and which types are spreading. Whatever the season, the yearly flu shot is the best way to lower your risk.

Can you have flu A and B at the same time?

Yes, though it is rare. You can catch influenza A and influenza B at the same time, or one soon after the other, because they are different viruses and protection against one does not cover the other.

Can a doctor help with flu virus B?

Yes. A doctor can assess your symptoms, check whether you are at higher risk, and decide whether antivirals would help; treatment is no different for type A or B. Medio's GPs consult by phone, and the doctor can discuss time off work and whether a medical certificate is appropriate.

What flu is going around right now?

It changes from season to season. Influenza A strains often lead early in winter, and influenza B is often more common later in the season. Your state health department's flu reports show which types are spreading now.

What's the difference between flu and cold?

Flu causes a sudden high temperature, pain all over and exhaustion, and the influenza virus behind it can make you very unwell. A cold builds slowly, mostly affects the nose, and rarely brings a high temperature.

Should I lay in bed all day with flu?

Rest as much as you need, in bed or on the couch, while you have a fever. Getting up to drink, eat a little and move gently is fine. Is influenza B contagious? Yes, for about a week, so stay home until you feel well.