Influenza continues to inflict an important burden on health-care systems. The 2009 H1N1 influenza virus first appeared in Mexico and the United States in March and April 2009 and has swept the globe with unprecedented speed.

The aim of this study is to evaluate effect of supplement vitamin on the clinical course of patients with acute respiratory illness suspected novel H1N1 infection.

Patients with acute respiratory illness randomized to control or vitamin groups. The patients completed questionnaire about their initial symptom scores. After 5 days of vitamin trial, patients were asked about their symptom by telephone survey.

Inclusion Criteria:

• Age > 20 years
• Acute respiratory illness suspected H1N1 infection
• Acute febrile respiratory illness(BT > 37.8) and throat pain or cough or nasal congestion

Exclusion Criteria:

• Pregnancy
• Hypersensitivity to vitamin A
• History of liver disease or renal disease
• Urinary stone disease