Signs and symptoms of upper and/or lower respiratory tract infection, along with systemic involvement in the form of fever, myalgia, and headache, are usually the main presenting features of the disease. In the context of an outbreak, otherwise healthy subjects presenting with a self-limited acute febrile respiratory illness usually require no further diagnostic procedures. In two retrospective studies that examined which clinical signs and symptoms are most predictive of influenza infection in patients with influenza-like illness, cough and fever were the only symptoms significantly associated with a positive PCR test for influenza [3, 4] . In another study, no isolated symptom or sign was able to accurately predict influenza infection, though the absence of fever, cough and nasal congestion significantly decreased its likelihood [5] . In general, patients diagnosed with pandemic H1N1 influenza A virus had similar signs and symptoms compared to those with seasonal influenza. However, these patients had gastrointestinal manifestations more frequently [6, 7] , were more likely to have pneumonia [8] , and also had higher rates of extrapulmonary complications, intensive care unit admission, and death [9] .