What is the name of this movie?

Okay, so basically what I remember from watching it awhile ago was that a new unknown disease is spread around this town. The story is mainly around a husband and a wife (the actress is blond I think). For some reason everyone who has been outside needs to stay outside, so the woman can't get in her house. She's potentially sick (I remember her coughing a lot), she saves a boy. The end of the movie is the wife and the husband talking trough the door, some people come and take her away. Then they seal the house and poison the man with gas or something because it appears he's the one who caught the disease. He manages to escape, but it's too late and he colapses on the ground.