Influenza B symptoms can occur quite quickly, sometimes seemingly appearing overnight.

Lasting around about three to seven days. These symptoms include:

Fever, sometimes as high as 106 degrees F (children tend to experience higher fevers than adults), fatigue, body aches, respiratory, cough, runny nose, sore throat.

These become more pronounced as the fever subsides, stomach irritation, including loss of appetite, vomiting, and nausea.

Influenza-A also causes most of the same symptoms listed above.

Influenza C generally only causes a mild fever or cold-like symptoms, if any.

Influenza B complications, pneumonia: viruses and bacteria do not normally work together, but sometimes influenza B can damage the lungs enough to make them more vulnerable to getting colonized by bacteria.

The resulting infection causes swelling, inflammation, and fluid buildup that can cause shortness of breath, chest pain, coughing, and fever.

Pneumonia is the most common influenza B complication and is most likely to strike the elderly or those experiencing another chronic illness.

Encephalitis: This is a form of brain inflammation that can rarely be cause by influenza exposure. It presents with headaches, fever, confusion, and drowsiness but can advance into seizures, fainting, or coma.

Myositis: This is a form of muscle weakness and inflammation that can be brought on by certain viruses, among other causes, and mostly affects children.

Main symptoms include difficulty moving the legs, weakness, and tenderness in the affected area.

Other Infections: In the same way as influenza B can make you more vulnerable to pneumonia, it can also make you more susceptible to bronchitis, sinus infections, and ear infections.

These are unpleasant, but fortunately far less serious ailments than pneumonia, though they share the same at-risk groups.