Types A and B are further divided into different subtypes based on the chemical structure of the virus. These subtypes are responsible for the outbreaks of flu. Influenza is highly contagious. Touching smooth surfaces such as doorknobs, handles, and telephones are other ways to catch the virus. 4 of 12 Symptoms may begin 2-3 days after exposure to the virus.
Flu comes on quickly and attacks the upper respiratory system.
Other family members or close contacts often have a similar illness. In younger children, the pattern of influenza may be a typical influenza-like illness or look like other respiratory tract infections such as croup, bronchitis, or pneumonia. Abdominal pain, vomiting, and diarrhea are frequently observed in children. Vomiting tends to be more significant than diarrhea. In infants, flu often goes unrecognized because the signs and symptoms are not specific and may suggest a bacterial problem.