Influenza
Overview
Influenza, commonly known as the Flu, is an infectious disease caused by an influenza virus. The disease is characterized by a sudden onset of high fever, cough (usually dry), headache, muscle and joint pain, severe malaise (feeling unwell), sore throat and runny nose. The cough can be severe and can last 2 or more weeks. Most people recover from fever and other symptoms within a week without requiring medical attention. But influenza can cause severe illness or death in people at high risk.
Types of Influenza Viruses
There are four types of influenza viruses: A, B, C and D. Human influenza A and B viruses cause seasonal epidemics of disease (known as the flu season) almost every winter in the United States. Influenza A viruses are the only influenza viruses known to cause flu pandemics, i.e., global epidemics of flu disease. A pandemic can occur when a new and very different influenza A virus emerges that both infects people and has the ability to spread efficiently between people. Influenza type C infections generally cause mild illness and are not thought to cause human flu epidemics. Influenza D viruses primarily affect cattle and are not known to infect or cause illness in people.
Influenza A Virus Subtypes
Influenza A viruses are divided into subtypes based on two proteins on the surface of the virus: the hemagglutinin (H) and the neuraminidase (N). There are 18 different H subtypes and 11 different N subtypes. Subtypes can be further broken down into different strains. Current subtypes of influenza A viruses found in people are influenza A (H1N1) and influenza A (H3N2) viruses.
Influenza B Virus Lineages
Influenza B viruses are not divided into subtypes, but can be broken down into lineages. Currently circulating influenza B viruses belong to either B/Yamagata or B/Victoria lineage.
Influenza Symptoms and Complications
Influenza viruses can cause mild to severe illness, and at times can lead to death. The flu is different from a cold. Flu usually comes on suddenly and may include these symptoms: Fever or feeling feverish/chills, Cough, Sore throat, Runny or stuffy nose, Muscle or body aches, Headaches, Fatigue (tiredness), Some people may have vomiting and diarrhea, though this is more common in children than adults.
Influenza Transmission and Prevention
Influenza viruses spread mainly by tiny droplets made when people with flu cough, sneeze or talk. These droplets can land in the mouths or noses of people who are nearby. Less often, a person might get flu by touching a surface or object that has flu virus on it and then touching their own mouth, nose or possibly their eyes.
The best way to prevent flu is by getting vaccinated each year with a Flu vaccine. Good health habits like covering your mouth when you cough and washing your hands often can help stop the spread of germs and prevent respiratory illnesses like flu.
Influenza Treatment
Antiviral drugs are prescription medicines that fight against flu in your body. Antiviral drugs are not sold over-the-counter. You can only get them if you have a prescription from a healthcare provider. Antiviral drugs are different from antibiotics, which fight against bacterial infections.