Antimicrobial therapy may be more beneficial when a treatable pathogen is identified than when a treatable pathogen is not identified. For exam- ple, anti-influenza agents (including oseltamivir and zanamivir) decrease the duration of symptoms by approximately 1 day and result in an earlier return to normal activity (by 0.5 day) among pa- tients with infections caused by susceptible virus- es. Prompt antibiotic treatment of patients with pertussis is indicated to limit transmission, but (with the possible exception of therapy initiated during the first week of symptoms) there are no compelling data to support the prospect that cough will be less severe or less prolonged with antibiotic therapy. Similarly, although several class- es of antibiotics have in vitro activity against M. pneumoniae and C. pneumoniae, it is unclear whether antibiotic treatment of bronchitis linked to these organisms influences outcomes. Table 1 includes suggested antimicrobial therapy for cases in which such therapy is considered.