GAD1 and diabetes mellitus: The type of diabetes was not identified in most of the case reports except for one patient who had undetectable serum C‐peptide levels after glucagon administration, suggesting a diagnosis of type I diabetes with no endogenous insulin secretion; however, this patient also did not have detectable anti‐GAD or anti‐IA‐2 antibodies, the presence of which can be helpful in the diagnosis of late autoimmune diabetes in adults.219 The relationship between diabetes and influenza infection is also supported by epidemiologic evidence from the Netherlands.