H7N9 Incident, immune status, the elderly and a warning of an influenza pandemic.

The novel re-assortment A influenza H7N9 (nrH7N9) emerged in humans in the Shanghai and surrounding provinces of China in late February and early March. Three infected index patients developed severe viral pneumonia with acute respiratory distress syndrome (ARDS) and resulted in fatal outcome. As of 15 April 2013 there were reported 60 confirmed nrH7N9 infections with 13 fatalities. Human-to-human transmission has not been observed, but zoonotic infections of nrH7N9 from birds to humans appear to be associated with live poultry markets. Elderly patients greater than 60 years of age accounted for 61% of the cases, indicating that the elderly may be at high risk for severe disease.