Outside of Roanoke, Virginia, health officials scramble to find the origin of a deadly bacterial outbreak of pneumonia.

Health officials in Albuquerque, New Mexico face an outbreak of a rare and fatal blood disorder. Patients suffer sharp muscular pain, fatigue, fever and rashes. Twenty-one people die from the illness. Five other states report similar cases. The epidemic is spreading. The Center for Disease Control assists federal and state health officials in their hunt for the cause.

In late August of 1999, an infectious disease specialist in Queens, New York reports that she has two elderly patients with neurological disorders. More cases crop up in the following days, several patients die. Initial tests confirm that New York has been hit by an outbreak of the mosquito-borne illness, St. Louis encephalitis. Nearly a month later, exotic birds begin to die at the Bronx Zoo.

In August of 1998, Marilyn Miller is awakened by her son's frightened cries. She finds him suffering from a dangerously high fever and severe abdominal pains. As doctors work to stabilize him, she begins to feel the sickening symptoms herself. Doctor's suspect a food poisoning outbreak and direct her to call the Minnesota Department of Health.

On the tiny resort island of Martha's Vineyard, landscaper, Patrick Ryer, suffers from chills and high fever. Patrick has contracted Tularemia, a rare bacterial disease. Health officials alert residents and tourists who crowd the Vineyard over the summer holiday. Over the next month, ten more people are diagnosed with the disease, including other landscapers and children.

A hospital in Walkerton, Ontario is flooded with patients with the same alarming symptoms. All suffer from fever, nausea and gastrointestinal problems. Health officials suspect water contamination, but the Public Utilities Commission (PUC) reports that the water is safe. The next day, 20 more patients are admitted with the same symptoms.

In the summer of 2001, Debby Stoner's family begins to exhibit severe flu like symptoms. Upon visiting the family, who live in a small village on Maui, doctors discover that others are also suffering from strange symptoms including headaches, fevers and a bizarre red rash. Health officials are concerned they are dealing with a terrifying virus that is spread by mosquitoes.

For months, members of the McGuire family suffer from chronic illnesses, bronchitis, pneumonia and abdominal pains, fever and chills. When Amy McGuire's respiratory ailments don't respond to any treatment, her parents become alarmed. Amy's mother watches a report on television warning of the dangers of mold in houses.

During December of 1999, public health authorities in Alberta, Canada are notified of two cases of a rare form of bacterial meningitis. A third reported case claims the life of a seventeen-year-old. Soon after, six more cases are reported and another young life is taken. Health officials think a new strain of the bacteria may be invading the population.

In December of 1979, a young girl passes out on a bus in Wisconsin. She is taken to the hospital complaining of a sore throat, fever and aching muscles. Doctors believe she has the flu, until her blood pressure drops and her kidneys begin to fail. When additional women begin exhibiting similar symptoms, which bring them close to death, doctors fear an outbreak of toxic shock syndrome.

Canadian doctors are alarmed when a middle-aged woman dies of cryptococcal meningitis in 1999. Over the next few years, doctors see dozens of similar infections with pneumonia-like symptoms including shortness of breath, weight loss and severe headaches. Vancouver Island becomes home to the largest outbreak of the deadly fungus anywhere in the world.

In 1993, aquatic researcher Joanne Burkholder suffers an array of troubling symptoms while working in her North Carolina State University lab. A fellow researcher confides that he has recently been plagued by bizarre medical problems including memory loss, confusion, numbness and a burning sensation on the skin, symptoms identical to Burkholder's.

When an unpredictable germ terrifies Texas in 1998, the CDC and health officials alert all neighboring states and territories to be on the lookout for streptococcus outbreak, the same bacteria that causes strep throat. This new strain, however, will kill 33 people, causing flesh-eating viruses, introducing deadly toxins into the blood and introducing pneumonia.

A classic case of Munchausen Syndrome by Proxy, Genene Jones killed at least 47 patients with the muscle relaxant succinylcholine while working at Bexar Medical Center in Texas. She loved creating emergencies, the excitement of a ""code blue"" and especially the reactions of family members when told of the death of a loved one.

Nine hundred children are sent home from school and thousands inoculated during an outbreak in Massachusetts that depletes local supplies of antibiotics and lands four middle school students in the hospital. Ten-year-old Kayla St. Pierre spends ten days in critical care and loses all of her fingers and both legs to the disease.

An unassuming male nurse from Kentucky comes under scrutiny when hospital officials notice that death is unusually prominent during his work shifts. In fact, death seemed to follow Donald Harvey from job to job, beginning in 1970 and ending with his arrest in 1987.

Dr. Harold ""Fred"" Shipman was known as a dedicated, hardworking and community-minded doctor who spent his life gaining the trust of his patients and the respect of his colleagues. And for 25 years, nobody suspected that the town doctor was amassing a death toll that would make him one of history's most prolific serial killers.

Reverend Dwight Moore is at death's door when he is transferred from his local hospital to Memorial Hospital in Chapel Hill. With all the expertise and technology of modern medicine at their disposal, doctors are still unable to find of the cause of Moore's symptoms, which include stomach pain, numbness, and hallucinations.

In an exclusive Kansas City suburb, cardiologist Mike Farrar is suddenly stricken with a powerful and mysterious stomach illness. The violent and terrifying symptoms are relentless, leaving the man fighting for his life. Mike's doctors fight to save him, but they struggle to find the source of the disease that is making him waste away before their eyes.

Phil Rouss realizes a lifelong dream when he opens an antique auto restoration business with his long-time friend Steve White. They divide the work - Rouss will restore the cars and Steve will handle the books. The business is an immediate success, but within weeks Rouss is struck down with a mysterious illness.

Robert Curley is newly married and is renovating an old home for he and his wife, Joann. He is also an electrician doing repair work in a local chemistry lab. Within weeks of starting the new projects he becomes violently ill. His feet and hands tingle for no apparent reason. Doctors diagnosis his ailment and send him home with medication, but that doesn't work.

Donna Boley of St. Louis, Missouri, has suffered flu-like symptoms for months. One day she's rushed to the hospital with organ failure and becomes paralyzed from the neck down. Tests show astronomical levels of arsenic in her urine.

When two young children in Idaho are diagnosed with food poisoning, doctors have no idea that within days the situation will get out of control, as two hundred thousand people fall ill in the country's largest case of single source food poisoning.