It is believed that cytokine storms were responsible for the disproportionate number of healthy young adult deaths during the 1918 influenza pandemic, which killed 17 to 50 million people. In this case, a healthy immune system may have been a liability rather than an asset. Preliminary research results from Taiwan also indicated this as the probable reason for many deaths during the SARS epidemic in 2003. Human deaths from the bird flu H5N1 usually involve cytokine storms as well. Cytokine storm has also been implicated in hantavirus pulmonary syndrome.