A New York, un homme d'affaires s'évanouit alors que sa peau devint bleu. A l'hôpital, d'autres patients arrivent avec les mêmes symptômes. L'équipe est appelée pour éviter une épidémie. Miles, le nouveau de l'équipe est envoyé dans un autre hôpital pour essayer de démonter qu'un bébé n'est pas victime de maltraitance.

Quatres jeunes filles dont le comportement est grégaire tombent toute dans le coma. Lors de l'enquête l'équipe se rend compte d'une activité sexuelle qui en serait responsable.

Sur une île de villégiature des Bahamas, un mal inconnu terrasse certains des clients du club. L'équipe est appelée et essaie par tout moyen de maintenir la quarantaine pour éviter que l'épidémie, si épidémie il y a, s'étende au territoire américain.

Des enfants d'une petite ville sont atteints d'un mal inconnu. L'équipe se tourne vers l'usine qui a déjà eu des démêlés avec l'EPA (l'agence gouvernementale environmentale). Ils se rendent compte que tous es enfants atteints sont des enfants in vitro et se tourne vers la clinique d'infetilité qui s'est occupée de ses fécondations mais ne trouve rien.

Dans les douches du centre sportif d'une université, un des athlètes convulse, en allant chercher de l'aide son ami se rend compte qu'un autre athlète a les mêmes symptômes dans les vestiaires. L'équipe naturellement recherche des traces de drogues synthétiques telles que le GHB avant de découvrir que d'autres étudiants sont atteints du même syndrome alors qu'ils n'ont aucun lien avec le sport.

The team flies to Philadelphia to figure out if Anthrax is showing up as a result of terrorism or not.

Les habitants d'une petite ville succombe à un virus inconnu. L'équipe est appelée après que le docteur décède.

After the victims of a car accident are diagnosed with a deadly disease, which caused the accident, a small Maryland town requests the assistance of the NIH team. The only problem is there is only one living victim, as the other nine victims had perished, and in order to save her life, and find the cure, she requires a bone marrow transplant. This little girls runs out of luck as her father has died from the same disease and her mother died from a drug overdose. However, Natalie does some DNA tests to see if the bone marrow can still be used, and discovers the girl was adopted. Eva then then goes and searches for the girl's birth mother, who wants no part in the girl's life. After some tough convincing, Eva gets the mother to donate, and saves the girls life. Now, in order to find the cause for the epidemic, the team must look to some tainted seafood for the answer.

When the adult film stars in Los Angeles start falling prey to a devastating disease, the hospital summons the assistance of the NIH team. At first, being as they are adult film stars, Connor suspects an STD. However, when the perfect housewife also falls prey to the same illness, a new link is needed to be found. After some testing, it is discovered that all of the women used the same plastic surgeon for breast implants. The team contacts the doctor, who is reluctant to help, but finally convince him to abide. The team tests the implants, but finds nothing. After some tough thinking, the team realizes that some fish and some water hold the answer.

An ""Angel of Death"" runs amok in a hospital, spreading a deadly flesh eating virus, which kills patients. Now it is up to the NIH to stop this lunatic, who has a past that they should not be proud of.

A surfer and volleyball player from a seaside town catch a mysterious disease. Dr. Connor and his staff begin suspecting that nearby seals played a part in this illness, however are the other forces at play?

A smallpox outbreak sends the NIH team to Montana. However, is this once thought to have been eradicated disease caused by terrorism, or is it natural?

The team is trapped in a snowstorm in the arctic while trying to figure what is causing pneumonia in patients that also causes psychosis. To make matters worse, one of their own goes down with the same illness.

The team travels to Baltimore to help stop an outbreak of the plague, a disease that wiped out much of Europe in the middle ages. But they uncover a string of dirty cops, who were trying to cover up a murder, in the process.

Split cases find Connor, Natalie, and Powell in New York City trying to cure victims who are presenting paralysis as a result of the September 11 Terrorist Attacks, and Miles and Eva down south trying to figure out what is causing the pregnant wives of military men to miscarry.

Une épidémie du virus Marburg a éclaté à ew York. L'équipe du NIH aidée de la police de New York, recherche le patient zéro.

Cross-over avec New York 911 dont [1/2] diffusée dans l'épisode 16 de la Saison 6 de cette dernière

Le mari d'une amie de Natalie tombe malade. Elle décide de l'aider mais avec les analyses, ils se rendent compte qu'il a attrapé une maladie vénérienne.

Connor and Powell must travel to a small Mexican town after an earthquake strikes, trapping Natalie, Eva, and Miles. Only when they go after Miles, who was trapped in the church Mission La Roca, they are captured by insurgents.

The team figures out that they are dealing with bacterial meningitis, and the only thing that makes their day worse is a corrupt politician who steals the medicine and holds it at ransom. Elsewhere, the people at Mission La Roca (Miles, Connor, Powell, Nestor, Juan, Kris, and Baracas) make it out before the church collapses, and take the sick ones off to the hospital for treatment.