The six-year-old girl at the children’s hospital in Lubbock, Texas, burned with fever and struggled to breathe. Doctors soon put her on a ventilator, snaking a thick tube down the child’s throat so a machine could breathe for her; they placed IVs to rehydrate her tiny body and they prescribed antibiotics for any bacterial infections that may have taken hold in the weeks she had spent at home battling measles.

But it was too late. Within a day of being ventilated, the child went into shock, her blood pressure crashed and she went into cardiac arrest. She could not be resuscitated. Her family, and the nation, mourned: she was the first child to die of measles in the US in a decade.

Yet some anti-vaccine activists soon began claiming that the girl died from medical malpractice, not measles, revealing a playbook that they are now running in Pennsylvania amid a growingoutbreak – a message taken up by Robert F Kennedy Jr, secretary of the US Department of Health and Human Services (HHS) and a longtime anti-vaccine activist, as he publicly disputes the rising death toll.