Would a dead rat in an air vent eventually kill a family?

Because I have a friend, and a dead rat was in his air vent, and the maintenance man said he can only cover that one air vent with a trash bag. That smell went away a few months ago. Now he is starting to get headaches, dizzy, weak, tonsil swollen, nymph nodes swell, almost every week. then he feels fine when he leaves the house. Is this serious, or is it Seasonal allergies. The same situation happens with his mom.

Sounds like allergies. If it was the rat would have happened sooner.

That person is probably just allergic. I'm allergic to dogs, so when I moved into my new house that used to have dogs in it, I got head aches and stuff until the air vents cleared up. He / she will be perfectly fine after about a month.

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