Influenza B is one of the primary viruses responsible for the seasonal flu. As a contagious respiratory illness, it targets the nose, throat, and sometimes the lungs. While there are four types of influenza viruses, types A and B cause the vast majority of illnesses in humans. Influenza B is significant because it circulates widely in human populations, contributing to a substantial portion of the flu cases each year.
Symptoms of Influenza B
The symptoms of Influenza B manifest suddenly and can be quite intense. One of the most common signs is a fever, which may be accompanied by chills. Individuals experience significant muscle or body aches, headaches, and a profound sense of fatigue. Respiratory symptoms are also a core feature of the illness, including a persistent cough, sore throat, and a runny or stuffy nose.
While these symptoms are common across all age groups, there can be differences in how the illness presents, particularly in children. Gastrointestinal issues, such as nausea, vomiting, and diarrhea, are more frequently observed in children with Influenza B than in adults. The combination of these symptoms can lead to a week or more of illness.
How Influenza B Differs from Other Respiratory Viruses
Influenza A and B viruses have distinct biological characteristics. Influenza A viruses are known for their potential to cause pandemics because they can infect a wide range of animals, including birds and pigs. This broad host range allows for significant genetic reassortment, creating new virus strains that can spread easily among humans. This gives Influenza A a higher mutation rate, evolving two to three times faster than Influenza B.
Influenza B, in contrast, primarily infects humans and mutates at a slower rate. Influenza B is categorized into two main lineages: B/Yamagata and B/Victoria. The co-circulation of these lineages has historically complicated vaccine development, though recent evidence suggests the B/Yamagata lineage may no longer be actively transmitting.
When comparing Influenza B to the common cold, the key differences are the severity and speed of symptom onset. Flu symptoms, including those from Influenza B, appear abruptly and are more severe. A common cold develops more gradually, with milder symptoms like a runny or stuffy nose being more prominent. While both can cause a cough, the flu often results in a dry cough, whereas a cold is more likely to produce mucus.
Transmission and Prevention
Influenza B spreads from person to person through respiratory droplets released when an infected individual coughs, sneezes, or talks. The virus can also be transmitted by touching a surface contaminated with these droplets and then touching one’s own mouth, nose, or eyes.
The most effective way to prevent infection is through annual vaccination. The flu vaccine is updated each year to protect against the strains of influenza viruses that are expected to be most common during the upcoming season. The quadrivalent flu vaccine is designed to protect against two influenza A strains and two influenza B lineages.
Beyond vaccination, practicing good hygiene is a practical way to reduce the risk of transmission. This includes frequent and thorough handwashing with soap and water or using an alcohol-based hand sanitizer. It is also helpful to avoid touching your face, especially your eyes, nose, and mouth. If you do become sick, staying home can prevent the spread of the virus to others in the community.
Treatment and Potential Complications
For most healthy individuals, managing Influenza B involves supportive care at home. This includes getting plenty of rest and drinking lots of fluids like water and broth to prevent dehydration. Over-the-counter medications, such as acetaminophen, can be used to relieve symptoms like fever and body aches.
In some cases, a doctor may prescribe antiviral medications like oseltamivir phosphate (Tamiflu). These drugs are most effective when started within the first 48 hours of symptoms and can shorten the duration of the illness and reduce the risk of serious complications. Antivirals are often reserved for individuals who are at a higher risk of developing complications from the flu.
While most people recover fully, Influenza B can lead to serious health problems. Common complications include pneumonia, bronchitis, and sinus infections. The flu can also worsen chronic medical conditions, such as asthma or heart disease. People at higher risk for these complications include young children, adults aged 65 and over, pregnant individuals, and those with weakened immune systems.