After a woman suffers having cysts surgically removed from her right breast, things get even worse when surgical sponges are accidentally left inside of her.

A dream vacation to South America becomes a nightmare when a man's face begins to be eaten away by a parasite.

Tara keeps feeling stabbing pains in her scalp, so she investigates the Internet for answers. What she finds is almost unbelievable - botflies. She decides to cut open her scalp.

Boil-like legions lead to a diagnosis of lung cancer, just in time for Christmas. But during surgery, doctors are surprised to find a different sort of infection.

Found in contaminated food and water, Entamoeba histolytica is a parasite that feeds on living cells in the human gut.

After eating some raw sushi, a woman begins a fight for her life as a mass containing parasitic worms creates a blockage in her colon. The woman has Anisakiasis, a disease caused by Anisakis worms.

A disease begins eating a boy's face from the inside, forcing doctors to begin removing the infected flesh to save his life.

A happily married couple's trip to New York becomes a nightmare when they learn that they have been infected with the Bubonic Plague, not only putting their lives in danger but anyone who comes into contact with them.

Leishmaniasis kills skin cells in mass numbers, causing prominent skin sores. In extreme cases, it attacks the face itself, leaving the victim disfigured.

The Leishmania parsite feeds directly on the vital organs from the inside-out. It's spread through infected sand flies.

Acanthamoeba is a voracious parasite that enters the body through the skin or the nose, then devours brain cells.

While swimming with a friend a man has a seizure and collapses. Shortly after, he finds out that a pork tapeworm has been slowly eating away at his brain!

Even dead, the larvae of parasitic roundworms can cause river blindness, or Onchocerciasis. These parasites are transmitted through the saliva of blackflies.

Burrowing through the skin and internal organs, gnathostoma worms can eventually cause paralysis and death.

The pork tapeworm is a particularly vicious parasite because it can end up in the most important organ in the human body: the brain.

A fitness fanatic cannot understand why he is too fatigued to work out until he learns an infection in his colon has created a tear, causing e-coli to spread through his body.

A happily married couple's trip to New York becomes a nightmare when they learn that they have been infected with the Bubonic Plague, not only putting their lives in danger but anyone who comes into contact with them.

A fitness fanatic cannot understand why he is too fatigued to work out until he learns an infection in his colon has created a tear, causing e-coli to spread through his body.

After suffering from an array of symptoms for months, Al Ceccarelli is diagnosed with Strongyloides, a disease caused by parasitic worms found in tropical climates.

When one woman checks a wound on her leg and sees a tube-like creature MOVE and retract into her body - she heads back to the doctor immediately.

After a woman suffers having cysts surgically removed from her right breast, things get even worse when surgical sponges are accidentally left inside of her.

After spending two months in a coma as a result of a Group A Streptococcus infection, Katy wakes up to the devastating news that all four limbs had to be amputated in order to keep her alive.

When a Dad and soldier has been hospitalized for extreme pain, jaundice and fever, doctors finally diagnose him with a very frightening parasite: 'Babesia.'

Lauren is a happy 7-year-old girl… until she begins suffering from tics, anxiety and manic episodes. Her symptoms build up to a terrifying breaking point.

A young woman's life has been deeply affected for five years by fatigue and illness, when the cause of Lyme Disease is finally discovered.

SNEAK PEEK: When a 15-month-old girl has a fever and bloody diarrhea, her frantic parents race her to the hospital. WHAT could be ailing this poor baby?

After complaining about pain on his head, 8-year-old Andrew is rushed to the ER, where doctors remove a botfly larva from his scalp.

It doesn’t look like Lizzie is the only person feeling sick around the house. What happens next to her husband, Anthony, has the couple feeling anxious.

When Zachary complains of pain inside his mouth, his parents look and find some mysterious blisters on his tongue.

When bacteria gains access to a woman's brain, it causes an abscess to grow that can lead to fatal results.

A woman's life is turned upside down when a mosquito infects her with an incurable virus, leaving her with no option but to wait and see if she lives or dies.

A man suffering from a deadly infection is medevaced to a hospital for emergency surgery to save his life. They discover dead tissue resulting from necrotizing fasciitis, a flesh-eating disease caused by the bacteria Streptococcus.