Diagnosis Unknown: In the Heart of Human Crisis

Health officials hunt for the source of an outbreak of Legionnaires' disease.

A fatal blood disorder kills 21 people in New Mexico and five other states.

After a specialist reports two patients with neurological disorders, further cases appear.

Apparently unrelated outbreaks of shigellosis baffle health officials.

Tularemia is on the government's watch list of bioterrorism agents.

An Ontario hospital is flooded with patients who have contracted a deadly strain of E. coli.

An outbreak of dengue fever infects nearly 200 people.

An investigation leads to a mold that causes pulmonary hemorrhaging.

A healthy 17-year-old model dies suddenly and Dr. Bullard suspects bacterial meningitis.

A healthy 14-year-old girl and two older women die from the same mysterious illness.

A middle-aged woman dies of cryptococcal meningitis, the first such death in British Columbia.

A community gets skin lesions and memory loss that eventually is linked to pfiesteria.

An invasive bacteria infects a baby in Texas, and doctors rush to save her.