How is flu season defined? what are the criteria for this definition?

The flu, also known as the influenza virus, is diagnosed year-round in the United States. Fall and winter seasons are when the greatest impact is usually seen and, therefore, is considered the "flu season." Influenza activity has a period of greatest activity between December and February, but the activity can last until May.

Every year at the beginning of the fall season, people are encouraged to get a flu shot.

CDC data on influenza vaccine:

• 116 million doses of influenza vaccines have been distributed.

CDC

(Centers for Disease Control and Prevention) recommends that all persons 6 months and older receive the influenza vaccine at the end of October.

• Influenza vaccination offers important benefits

explanation:

the sun shines white and black light to our planet. the white light has all the colors in it. in our upper atmosphere, we have dust particles and oxygen molecules. the white light meaning all of the colors in a rainbow shines through the upper levels of the atmopshere and the blue light scatters across the entire planet. that is why our sky is blue.