Influenza B is a viral infection that attacks parts of the respiratory system such as the nose, throat and lungs, according to MayoClinic.com. There are three types of influenza viruses: A, B and C. Type A is responsible for worldwide epidemics, Type B is localized and Type C is mild. People who contract influenza usually get the Type A or B strain of the virus. Complications are similar for both types of strains, although Type B tends to be milder than Type A, according to FluFacts.com.
Bacterial pneumonia is the most common and serious complication associated with influenza B. The influenza virus can damage the surface of the lungs, restricting the airway and increasing the risk of bacterial infections such as bacterial pneumonia, according to Solvay-Influenza.com. Bacterial pneumonia occurs when harmful bacteria rapidly increase inside the respiratory tract causing swelling, fluid and inflammation within the air sacs in the lungs. Once a person's lungs fill with fluid she may have a hard time breathing, resulting in a stabbing chest pain, shortness of breath, high fever and coughing, according to the website Bacterial Pneumonia. Bacterial pneumonia can be life-threatening for the elderly and people who have a chronic illness such as cardiovascular and lung diseases.
A rare complication associated with influenza B is encephalitis, according to the website NHS Choices. Encephalitis typically occurs when the brain becomes inflamed as a result of a viral infection such as influenza B. Encephalitis can occur when the immune system becomes overly stimulated from fighting the influenza virus, according to The Merck Manuals of Health and Aging. Fever and headache are usually the first signs of the condition immediately followed by seizures, confusion, drowsiness, loss of consciousness or coma. NHS Choices states that encephalitis can affect people of all ages, but children younger than 7 and adults older than 55 are extremely susceptible to infection.
A common complication of influenza B that primarily affects children is myositis, or muscle inflammation, according to Solvay-Influenza.com. Symptoms of myositis include leg pains and muscle tenderness that last between one and five days. The influenza virus can inflame the muscles in the body that are responsible for movement, causing muscle weakness and pain when walking or moving.
A small number of children or adolescents who are recovering from influenza B may develop a neurological disease called Reye's syndrome, according to The Foundation for Better Healthcare. Reye's syndrome usually begins with nausea and vomiting and quickly progresses into confusion or delirium. Some children or adolescents may experience this disease following the ingestion of aspirin for the pain and fever associated with influenza. The Foundation for Better Healthcare states that fewer than three children per 100,000 with influenza go on to develop Reye's syndrome, but it is always wise to consult a physician before administering aspirin to children.