Adjunctive Sirolimus and Oseltamivir Versus Oseltamivir Alone for Treatment of Influenza

Inclusion Criteria: * influenza A and B virus infections confirmed by PCR and/or immunofluorescence assays, hospitalized for the management of severe manifestations of influenza, initiation of oseltamivir, clinical evidence of lower respiratory tract infection (e.g. shortness of breath, tachypnea, oxygen desaturation, crepitations on auscultation, infiltrations or consolidations on chest radiograph) and written informed consent (by the subjects, or from their next of kin if the subjects are unable to provide written consent at the time of enrollment) Exclusion Criteria: * use of other immunosuppressants (e.g. post-chemotherapy, post-transplant, autoimmune diseases) other than systemic corticosteroids * patients with known immuno-compromised conditions (e.g. active haematological malignancies, HIV/AIDS patients who are on antiretroviral therapy and CD4 cell count \< 200) * pregnancy/lactation * hepatic failure * patients with surgery done/planned within 1 month * patients who have received macrolide antibiotics and NSAID for 1 week prior to enrolment due to their immuno-modulating effects * patients on drugs that may interact and alter sirolimus level (rifampicin, azole antifungals, phenytoin, diltiazem, verapamil, nicardipine, metoclopramide, phenobarbital, carbamazepine) will be excluded for safety purposes * Use of investigational anti-influenza antivirals and blood products