Influenza, commonly known as the flu, is a contagious viral infection that affects the respiratory system. It can cause a range of symptoms, including fever, chills, cough, sore throat, muscle aches, fatigue, and headaches. Influenza is typically more severe than the common cold and can lead to complications such as pneumonia, particularly in vulnerable populations such as young children, elderly individuals, and those with weakened immune systems. The flu virus spreads easily through respiratory droplets when an infected person coughs, sneezes, or talks. It can also be spread by touching a surface contaminated with the virus and then touching your mouth, nose, or eyes. There are 4 main types of influenza viruses that affect humans: influenza A, influenza B, influenza C and influenza D. The influenza A virus has a subtype known as H3N2, which can induce sickness in humans and animals such as pigs and birds. This particular strain of the flu virus is capable of causing illness. During the testing process, respiratory specimens such as nasopharyngeal swabs or nasal washes are analyzed to detect viral RNA or antigens.