The Nassir family is a Syrian family living in America. Most of their members are unnamed in the series.
- Sayid Nassir, first believed to be Patient Zero and a bioterrorist. He arrived on Monday illegally and died on Day 1 of the outbreak.
- Radwan, Sayid's uncle.
- Lena, Radwan's wife.
- Unnamed teenager, who is Radwan and Lena's son, Sayid's cousin and Elizabeth Franklin's boyfriend. Portrayed by Ali Mahmood.
- Unnamed woman, who is Sayid's grandmother and Radwan's mother. Portrayed by May Hawawini Kaba.
- Unnamed woman
They are practicing Muslims; both Lena and her mother-in-law wear the hijab and Radwan wears a taqiya. They are also conservative, as Sayid's grandmother tells Jake that her family wouldn't have approved of her teenager grandson having an American girlfriend.
In the morning of Day 1, Radwan takes his nephew Sayid, who has flu-like symptoms, to the hospital. Sayid refuses to stay for observation and they get back home. Although the first official version was that Sayid was already sick and infected Dr Sanders, it is actually the contrary as Dr Sanders had just been infected by her boyfriend.
Later, after the Police traces Sayid's steps, Jake, Walden and Jim Banks go to Radwan's house. Radwan first pretends not to know Sayid, and after Jake says he is not with Immigration he explains that Sayid is his cousin and he arrived on Monday. He brings them to the bedroom as Lena tries to warn Sayid; Jake then sees Sayid and his grandmother, both symptomatic. Both Sayid and the rest of the family are put into isolation.
Sayid Nassir dies at 16:29 and according to the IES several inside the home have foregone to exhibit early symptoms.
Cannerts says that he has all five remaining members of the family in isolation, and all have advanced symptoms. When Jake discovers about the teen's girlfriend, he asks him about her but he doesn't react; his mother Lena refuses to answer and asks him to leave them alone; Sayid's grandmother does answer to say that the teen didn't tell them because they wouldn't have approved. When the teenager sees Elizabeth in the corridor, he places his hand on the glass and she does the same on the opposite side before being put into isolation.
At the end of the episode, it is mentioned that 2 out of the 5 members of the family have died.
It is presumed that all of the remaining members of the Nassir family die during this episode.