Bird influenza is an emerging disease. If you were given the task of using Koch's postulates of finding the pathogen causing bird flu, what sequence of procedures should you use?

A. (1) Check whether the presence of the suspected pathogen correlates with the occurrence of symptoms, then (2) isolate the pathogen from an infected bird and grow it in pure culture, (3) inoculate cells from pure culture into a healthy host to see whether it causes the disease, and (4) attempt to isolate the suspected pathogen from the inoculated host.

B. (1) Isolate in pure culture the suspected pathogen from sick birds, then (2) use a series of medications to treat the sick birds, (2) select the medication that worked best, (3) apply that medication to pure cultures of the pathogen, and (4) see whether it kills the pathogen, compared to control treatments without the medication.

C. (1) Take blood samples from a sick bird, (2) isolate the pathogen in pure culture, (3) treat the bird for the disease and when it recovers take a second blood sample, and (4) test the blood to check whether it no longer contains the pathogen.

D. (1) Inoculate a healthy bird with the suspected pathogen to see whether it becomes sick, (2) compare symptoms of that bird with those from a bird known to have the disease, (3) isolate the pathogen from both birds in pure culture and stain them to see whether they are both Gram-positive, and (4) make a vaccine from the pure culture of one bird and inject it into another to see if it recovers.

E. (1) Inject a bird with the suspected pathogen, (2) inject another bird with a control that doesn't contain the suspected pathogen, (3) repeat with more birds, and (4) plate out samples of blood from both kinds of birds to see if you can isolate the pathogen in pure culture.