Influenza

Article submitted by Irene Hodge from the Allegheny County Health Department.

Influenza (the flu) is caused by a virus that infects the nose, throat, and lungs and is spread by respiratory droplets from coughs and sneezes. It is an infection that may cause severe illness and life-threatening complications in many people. Flu symptoms include fever, chills, headache, extreme fatigue, dry cough, sore throat, and muscle aches. Children can also have nausea, vomiting and diarrhea, however these problems are not common in adults.

In the U.S., the flu occurs seasonally from late fall and peaks anytime in late December through March. The flu season usually tapers off by April, but there can be occasional infections into the summer months. Health officials collect data on influenza year round and report on flu activity October through May. There are tow main types of influenza viruses that circulate each season (type A and B), and there are variant strains within each type. The same flu strains do not necessarily circulate each year which means that the influenza vaccine must be prepared according to which strains are dominant each season.

People aged 65 and older and persons of any age with chronic medical conditions are highest at risk for flu complications and thus are high priority for receiving influenza vaccine. Children under age two and pregnant women are just two groups for whom recent research also supports recommending annual flu vaccination. Influenza seasons are unique. However estimates show that each year, about 5 to 20 percent of Americans come down with the flu, more than 200,000 are hospitalized with complications, and 36,000 people die.