Influenza (flu) generally refers to the illness that results from infection with one of the influenza viruses. There are two primary types of human influenza viruses (A and B).
Cases Per Year (US)
Tens of millions of people in the US get the flu each year. The highest incidence in recent years was during the 2017-18 flu season, when 49 million cases of flu were reported to the CDC.
The flu occurs worldwide. In the northern hemisphere, it affects approximately 5-15% of the population annually.
The flu is spread through respiratory droplets, which means that anyone near a person carrying the flu virus is at risk. Importantly, the virus replicates for a day or two before symptoms start, so people can be contagious when they seem healthy.
What are the symptoms of influenza?
Flu has a few cardinal symptoms–cough, fever, fatigue, and body aches. These often develop rapidly, without warning. Some people have a variety of associated symptoms, such as sore throat, runny nose, vomiting, and diarrhea, but those are more common with other, non-flu viruses. In the absence of cough, fever, and body aches, mild symptoms of an upper respiratory tract infection (like runny nose and sore throat) are indicative of a cold and not the flu.
What time of year or season is influenza most commonly spread?
Flu is most predominant in fall and winter. The period between October and March is generally considered to be “flu season.” Peak months are typically December, January, and February, though in some years there are still many cases of flu as late as May.
Additional Preventive Measures
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Andrew Cunningham, MD and Nora Lansen, MD are both members of the Galileo Clinical Team. Connect with one of our physicians about Flu or any of the many other conditions we treat.Join Today