Cаse Study: Twо Unusuаl Pаtients Part A: The Unknоwn Viral Infectiоn A public health laboratory receives a respiratory sample from a patient with severe pneumonia. Initial bacterial cultures are negative, and the microbiologist suspects a viral infection. To identify the pathogen, the laboratory inoculates a mammalian cell culture with the patient's specimen. After several days, the cells begin to round up, detach from the culture dish, and die, indicating a cytopathic effect (CPE). Another laboratory working on the same outbreak studies the virus by infecting laboratory mice to observe disease progression and immune responses. The physician asks the laboratory director why different methods are being used to grow and study the virus. 1. Which method used in this case is an example of an in vitro viral cultivation technique? [Question1] 2. Which method used in this case is an example of an in vivo viral cultivation technique? [Question2] 3. What is one advantage of using cell culture (in vitro) to study viruses? [Question3] 4. Why might researchers still use an in vivo model such as mice? [Question4] Part B: The Progressive Neurologic Disease Several months later, a neurologist evaluates a 58-year-old patient with progressive memory loss, personality changes, poor coordination, and rapidly worsening dementia. Brain imaging shows degeneration of nervous tissue. Routine tests fail to identify bacteria, fungi, parasites, or viruses. The patient's family reports that years earlier the patient consumed meat from cattle involved in a region affected by bovine spongiform encephalopathy ("mad cow disease"). Researchers determine the illness is caused by an infectious agent that contains no DNA or RNA. 5. Which type of infectious agent is most likely responsible for this disease? [Question5] 6. What characteristic distinguishes prions from viruses? [Question6] 7. How do prions cause disease? [Question7] 8. Which route is most consistent with the suspected transmission described in this case? [Question9]