Respiratory infections are among the most common causes of morbidity and mortality worldwide.  These infections present a special challenge to physicians for several reasons, including of the recent disasters caused by severe acute respiratory syndrome (SARS) and bird and swine influenza, the increase in viral and bacterial resistance to currently available anti-microbial drugs, the increased frequency of new viral lung infections in clinical practice, and the worldwide emergence of deadly drug-resistant forms of TB.  For these reasons, it is important for infectious disease specialists to have an overview of emerging respiratory infections.