The purpose of this study is to determine the duration of viral shedding in hospitalized patients with influenza virus, treated with oseltamivir.

A prospective cohort study will be undertaken during the influenza season of 2015 in Rambam Medical Center, Haifa, Israel.

The study group will include inpatients older than 18 years, who have clinical presentation suggestive of influenza virus infection defined by the World Health Organization and the Center for Disease Control and Prevention, including sudden onset of high fever, cough, headache, muscle and joint pain, severe malaise, sore throat and runny nose, who were found positive to influenza virus by polymerase chain reaction test, and in whom anti viral treatment was indicated.

Exclusion criteria:

1. Immune compromised patients: patients after solid organ transplant, post bone marrow transplantation, with inherited or acquired immune deficiency, or patients treated chronically with immunosuppressive drugs.
2. Pregnant women.
3. Patients who were treated with oseltamivir in the previous 6 months.

Patients who approve their participation will to fill a questionnaire, and a polymerase chain reaction assay for influenza will be performed as follows:

The first sample will be taken right before the first dose of oseltamavir, and then on days 2, 3 and 5.

Samples will be stored at a temperature of +4 Celsius degrees for a maximum of 48 hours.

Outcomes: we will consider a positive polymerase chain reaction test 3 days after the initiation of treatment as prolonged shedding.

Inclusion Criteria:

1. clinical presentation that suggest influenza virus infection, including sudden onset of high fever, cough, headache, muscle and joint pain, severe malaise, sore throat and runny nose,
2. positive to influenza virus by PCR test
3. anti viral treatment was indicated

Exclusion Criteria:

1. Immune compromised patients: patients after solid organ transplant, post bone marrow transplantation, with inherited or acquired immune deficiency, or patients treated chronically with immunosuppressive drugs.
2. Pregnant women.
3. Patients who were treated with oseltamivir in the previous 6 months

Adults hospitalized and diagnosed with influenza