All four flu pandemics — in 1918, 1957 and 1968 and the swine flu pandemic of 2009 — were caused by Type A viruses. Influenza B viruses, however, only circulate in humans.

Influenza is a common respiratory virus that is categorized into four types: A, B, C and D. Type C only causes mild infections and type D is not believed to infect humans.

1918-19 "Spanish flu" A -- Caused the highest known influenza-related mortality: almost 700,000 deaths occurred in the U.S., and between 50 million to 100 million worldwide 1957-58 "Asian flu" A ...

Two types of influenza viruses are responsible for seasonal flu outbreaks: Influenza A and B. Influenza A accounts for around 75 percent of all cases and tends to cause more severe illness in adults.

The flu is a contagious viral infection of the respiratory system that affects the nose, throat and lungs. It is caused by influenza viruses. Symptoms of mild flu infections can resemble those of ...

Influenza A and B are the most common types of flu in humans. Here, learn about the differences between influenza A and B, including symptoms and treatments.

A doctor can usually tell if you have the flu based on your symptoms, especially if it’s during peak season. But they may want to give you a quick test to be sure the influenza virus is to blame ...

The isolation of influenza virus 80 years ago in 1933 very quickly led to the development of the first generation of live-attenuated vaccines. The first inactivated influenza vaccine was ...

As the Centers for Disease Control and Prevention (CDC) explains, bird flu is a disease caused by the influenza A virus. At the same time, recent CDC data shows that seasonal influenza A is rising ...

The flu is a contagious viral infection of the respiratory system that affects the nose, throat and lungs. It is caused by influenza viruses. Symptoms of mild flu infections can resemble those of ...

Influenza virus is an infectious agent belonging to the virus family Orthomyxoviridae that causes a respiratory tract infection (influenza or 'flu') in vertebrates. There are three main species ...

Researchers found that among 53,402 Cleveland Clinic employees in northern Ohio, getting the influenza vaccine was associated with a 27% increase in flu infections. BOOST YOUR IMMUNE SYSTEM WITH ...