, most people infected by this flu suffered a mild illness, but the small minority hospitalized were often severely ill. Arand Kumar, an intensive care expert at the University of Manitoba, Winnipeg, Canada, said "this pandemic is like two diseases; either you're off work for a few days or you go to hospital, often to the intensive-care unit (ICU). There's no middle ground." In the southern hemisphere 15 to 33% of hospitalized cases went to the ICU in July and August 2009. Unlike H5N1 avian flu and SARS which provoke a runaway body-wide immune response, H1N1/09 destroys the lungs' alveoli, often causing acute respiratory distress syndrome, which kills in half of all cases. Preliminary research suggests that severity is linked to a genetic variation in immune systems.
