How to determine whether it is influenza A or influenza B virus infection

Influenza A (H1N1) and influenza B are both acute respiratory infections caused by influenza viruses. Their symptoms are very similar and include fever, cough, sore throat, muscle aches, fatigue, and headache. Because these symptoms generally cannot be distinguished based on clinical presentation alone, specific diagnostic tests—such as viral isolation, respiratory virus antigen testing, or nucleic acid testing—are usually required to accurately differentiate between influenza A and influenza B.