Three main types of
influenza viruses cause the flu: Type A, Type B, and Type C.
All three virus
types are spread in the same way: they leave an infected person’s body in
droplets whenever that person coughs, sneezes, or puts their mouth on another
object. The Centers for Disease Control and
Prevention (CDC) report that a person with the flu can spread the virus to
others up to six feet away. If you are in close contact with an infected
person, you may end up inhaling infected droplets immediately. However, you can also pick up the virus later
from touching an infected object (such as a door handle or a pencil) and then
touching your eyes, nose, or mouth.
flu is highly contagious. Most people experience flu symptoms within one to
four days of getting sick. However, an infected person can begin spreading the
flu virus to others one day before manifesting symptoms, and for up to a week
after getting sick.
This is why it is
essential to maintain vigorous personal hygiene, especially during flu season.
This includes simple steps, like using antibacterial liquid to clean your hands
after getting off a bus, or washing your hands extra carefully before eating.
Such steps can go a long way when it comes to avoiding the flu and preventing
Type A influenza
virus is the most virulent form of influenza and the one that causes the most severe
illness. This virus often originates in populations of wild birds, poultry, or
swine (including pigs and hogs), so different strains are sometimes referred to
as avian (bird) or swine flu. Type A influenza is most active during colder
weather in temperate climates, and its peak season typically runs from late
fall to early spring.
Type A influenza
virus is categorized according to variations in two proteins on the surface of
the virus: H (hemagglutinin) and N (neuraminidase). According to the CDC, there are 17 subtypes of the H
protein and 10 subtypes of the N protein. Different protein combinations lead
to different strains of the virus. H1N1 and H3N2 are two recent strains of Type
A influenza virus.
The two most active
strains of Type A virus, usually H1N1 and H3N2, are usually included in each
year’s flu vaccine. If a new virus strain emerges that is not covered by the
annual flu vaccine, a special vaccine is made to combat the new strain of
The United States
government recommends that all
individuals six months and older get a yearly flu vaccine.
Type B influenza is
not divided into subtypes, but the virus does mutate into different strains.
Unlike Type A, Type B influenza is active throughout the year. Nevertheless, it
generally causes a much milder form of the flu than Type A viruses.
The strain of Type
B virus most active in the population is usually included in the annual flu
Type C influenza is
the least common type of the flu, and its symptoms are generally much milder
than those of Type A or B influenza. Type C influenza is not included in yearly