Bird flu may over-stimulate immune system HONG KONG, Nov. 11 (UPI) -- Researchers in Hong Kong say the H5N1 bird flu virus may provoke an excessive immune reaction, explaining why it is deadly even to the young and healthy. Laboratory tests on human cells showed that the virus caused the immune system to send proteins called cytokines to infected lung cells, a reaction that would end up damaging or destroying the tissues the immune system is meant to defend. The tests were carried out by scientists at the University of Hong Kong, working with samples from patients who died in...