Health records of 31 babies with pertussis in pediatric intensive care units in California between 2009 and 2011 revealed greater white blood cell counts and at least a 50% increase in white blood cells among nearly all of those with more severe pertussis. Aside from having elevated maximum heart and breathing rates, babies with more serious pertussis were more at risk for seizures, shock and kidney failure, researchers found. The findings appear in the Journal of the Pediatric Infectious Diseases Society.