H1N1, also known as the "swine flu," refers to a subtype of influenza A virus that caused a global pandemic in 2009. The H1N1 influenza virus is a combination of genetic material from pig, bird, and human influenza viruses.

The H1N1 influenza virus spreads among humans through respiratory droplets produced when an infected person coughs or sneezes. It can also spread by touching surfaces contaminated with the virus and then touching the face, mouth, or eyes.

The symptoms of H1N1 are similar to those of seasonal influenza and can include fever, cough, sore throat, runny or stuffy nose, body aches, headache, chills, and fatigue. Some individuals may experience gastrointestinal symptoms such as nausea, vomiting, or diarrhea. In severe cases, complications such as pneumonia, respiratory failure, and worsening of underlying medical conditions can occur.

The 2009 H1N1 influenza pandemic resulted in a significant number of illnesses and deaths worldwide. However, it is important to note that H1N1 is now considered a regular seasonal flu virus and is included in the annual influenza vaccine to protect against its circulation.

Vaccination is one of the primary ways to prevent H1N1 infection. The seasonal influenza vaccine typically includes strains of H1N1, along with other influenza viruses. Other preventive measures include practicing good hand hygiene, covering your mouth and nose when coughing or sneezing, staying home when sick, and avoiding close contact with individuals who are ill.

If you experience flu-like symptoms, it is recommended to seek medical attention, especially if you are at high risk for complications, such as young children, older adults, pregnant women, and individuals with underlying health conditions.​​