Also known as: R-pox
A teenage girl develops a severe pustular rash, high fever, and vomiting after scuba diving on a shipwreck. Initially suspected to be smallpox from an ancient sealed jar, the diagnosis is ultimately revealed to be rickettsialpox (transmitted by mice on the ship), which is treatable with doxycycline. Her stepfather dies before the correct diagnosis is made.
Also known as: Adverse reaction to smallpox vaccine
Julie's stepfather develops severe systemic vaccinia infection after receiving the smallpox vaccine. His immunocompromised state from recurrent kidney cancer makes him vulnerable to the vaccine virus itself, leading to widespread pustules, kidney failure, and death. House initially believes this proves it's not smallpox.
Also known as: Kidney cancer relapse
The stepfather's kidney cancer has returned after six years of remission, causing immunosuppression that makes him fatally vulnerable to the vaccinia virus from the smallpox vaccine. Blood in his urine catheter provides evidence of the cancer's recurrence.