Viewing Infectious Respiratory Disease begins by examining bacterial secondary infection following influenza virus infections. Influenza patients can develop secondary infections, leading to pneumonia which may be fatal. The video describes a model used to study the action of levofloxacin on airways mucosa. Mice were injected with influenza virus followed later by an injection of Streptococcus pneumonia. Levofloxacin was given in an oral dose equivalent to a once-daily clinical dose of 500 mg four days after administration of S. pneumoniae. A control group received no antibiotic. Two out of six mice in the untreated group had died 4 days after S. pneumoniae administration while all the mice in the levofloxacin group survived. Next, clinical results of levofloxacin (Cravit) in patients with infectious diseases are discussed. The reported efficacy was 95.1%.