Mouse serum cotinine levels at different time points.

<p>A) Serum cotinine levels during 21 days of cigarette smoke exposure. The serum samples were collected on day 7, day 14 and day 21 (immediately or 14 hours after cessation of cigarette smoke exposure). (n = 2 and n = 4 for air and smoke exposure group respectively). B) Serum cotinine levels of air or cigarette smoke exposed mice on day 1, day 5 and day 14 after pdmH1N1/H9N2 virus infection. (n = 2 and n = 4 for air and smoke exposure group respectively). C) Serum cotinine levels of sterile water or nicotine treated mice on day 0 and day 14 after pdmH1N1/H9N2 virus infection. (n = 4 for both sterile water and nicotine treatment groups). Results represent mean ± SEM.