What are flu and H1N1?

Also known as: influenza, seasonal flu, swine flu.

Flu is a very common, highly contagious, often severe viral illness that affects the respiratory airways (the breathing passages of the nose and upper and lower bronchial tubes, and lungs), that occurs during the winter months.

The influenza virus has a number of types called A, B and C. A and B cause epidemics, while type C usually causes no or mild respiratory tract symptoms. Influenza viruses continually change (mutate) which means every year many children’s (and adults’) immune systems are not equipped to manage it.

Different subgroups of influenza A (the most dangerous of the group) are named according to the the body’s immune response to their surface glycoproteins called HA and NA.: e.g. H1N1 (called swine flu), (plus another at least 15 different HA and 9 NA subtypes).


Reviewed by: Jose R. Rosa-Olivares, M.D.

This page was last updated on: 1/29/2019 3:21:13 PM

© 2021 Nicklaus Children's Hospital. All Rights Reserved.