Influenza is a highly contagious respiratory virus that affects the lungs, nose, throat and bronchial tubes. Most commonly referred to as the flu, influenza typically lasts for about a week, but in some cases it can be fatal. According to the Centers for Disease Control and Prevention (CDC), more than 200,000 Americans are hospitalized because of the flu each year.
Causes and Symptoms
The flu can spread through the air via droplets from coughing, sneezing or talking. The virus can also be spread through contact with objects that have these droplets on them, such as a telephone. The most common symptoms of the flu are fevers, coughing, sore throats, runny or stuffy noses, headaches, body aches, chills and fatigue.
Types
There are three different types of influenza viruses. Influenza Type A is responsible for causing seasonal epidemics and is divided into different subtypes based on two proteins, hemagglutinin and neuraminidase, that are found on the virus's surface. There are 16 different hemagglutinin subtypes and nine different neuraminidase subtypes. Type A virus can also be further divided into different strains. Currently, the most severe Type A strains are the bird flu (H5N1) and the swine flu (H1N1).
Type B influenza viruses can also cause epidemics but most commonly produces smaller outbreaks. The Type B virus is not divided into subtypes but can be divided into strains.
Type C influenza viruses are less common, are not covered in the flu shot, and do not cause any epidemics.
At Risk
The flu can affect people of all ethnicities, ages, genders and backgrounds. Those who are over the age of 65, infants under the age of two, pregnant women, individuals with weakened immune systems and individuals who have chronic illnesses like diabetes are considered at high risk for catching and developing complications from the flu.
Epidemics
According to the World Health Organization (WHO), there are an estimated 3 to 5 million annual cases of the flu worldwide. Of those cases, up to 500,000 people die each year from the flu. These epidemics generally take place during the fall and winter seasons, in temperate regions, and they can cripple an economy or an entire population.
Prevention
The CDC recommends a yearly flu shot as the first step in prevention. This yearly shot covers the three most common seasonal strains. For other strains not covered, like the swine flu, a separate shot is necessary. Other common measures of prevention are eating right, washing your hands often, regular exercise and avoiding sick people.
