Influenza (flu)

ARTICLE SECTIONS

Introduction Signs and symptoms Causes Risk factors When to seek medical advice

Complications Treatment Prevention Self-care

Introduction

Influenza is a viral infection that attacks the respiratory system, including your nose, throat, bronchial tubes and lungs. Although it's commonly called the flu, influenza is not the same as the stomach viruses that cause diarrhea and vomiting.

Anyone can get the flu, but young children, older adults, people with weakened immune systems and those with chronic illnesses are especially vulnerable. If you're at high risk of flu, your first line of defense is an annual flu shot. Although the shot doesn't offer 100 percent protection, it can reduce your chance of infection and help prevent serious complications if you do get sick.

Approximately 50 million people died worldwide in the 1918 influenza pandemic. Today, according to the Centers for Disease Control and Prevention, as many as 36,000 Americans die each year of complications of influenza and more than 200,000 are hospitalized.

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Signs and symptoms