H1N1 swine flu is a type of pandemic influenza that began circulating and caused a worldwide outbreak in 2009. It is caused by a specific strain of the influenza virus.
Cause
Occasionally, a strain of influenza that usually causes illness in one species of animal mutates and starts making humans sick. When this occurs, if transmission occurs easily between humans, it can cause a flu pandemic, even outside of the typical flu season. Since the early 20th century, flu pandemics have occurred approximately every 30 years.
H1N1 swine flu is a specific strain of the influenza virus that causes flu in pigs. In 2009, a new strain was found in humans that had not previously been seen. Officially, it is called influenza A (H1N1) pdm09 virus. This mutation and subsequent spread led to a pandemic that sickened millions of people worldwide and killed hundreds of thousands.
Risk Factors
Although anyone can get H1N1 swine flu, some people are more likely to be seriously affected by it. Seasonal influenza typically is most serious for older adults over the age of 65. However, the H1N1 swine flu pandemic disproportionately sickened and killed people under the age of 65.
It is believed that a majority of people over the age of 65 had some immunity to the H1N1 swine flu pandemic virus, which provided protection to those that would be at highest risk during a seasonal flu outbreak.
Current Risk
It’s also important to note that the strain of influenza that caused the H1N1 swine flu pandemic is still circulating.
While H1N1 was new in humans at the time of the 2009 flu pandemic much of the world’s population has now been exposed to it.
