👉 The Buchanan virus, also known as the influenza virus, is a well-known and highly contagious respiratory illness caused by the influenza A virus. It primarily affects adults over the age of 20 due to its high mutation rate and the potential for severe outcomes in those who are immunocompromised or have weakened immune systems. The virus is transmitted through coughing, sneezing, and close contact with infected individuals, causing respiratory infections such as colds, flu, and pneumonia.