An acute infection of the epiglottis, is usually caused by Haemophilus influenzae. The epiglottis becomes very swollen and may obstruct the airway. This is a rare but very serious condition which may rapidly cause death unless correctly diagnosed and rapidly treated. Children with acute epiglottitis also have a Haemophilus influenzae septicaemia. Acute epiglottitis due to Haemophilus influenzae can be prevented by Hib immunisation of all children. Do not confuse Haemophilus influenzae (a bacteria) with the influenza virus.