Pneumonia
From Wikipedia, the free encyclopedia. http://en.wikipedia.org/wiki/Pneumonia
Pneumonia is a medical condition that describes a
result of a variety of diseases in which the small, air-filled
sacs in the lung
responsible for absorbing oxygen from the atmosphere
are flooded with fluid. There are many different kinds of pneumonia, but the
most common type results from infection of the lung by bacteria,
viruses,
fungi,
or parasites.
Other types can occur as a result of chemical or physical irritation of the
lungs. Pneumonia is a common illness and occurs in all age groups. Pneumonia is
a leading cause of death
among the elderly and people who are chronically ill.
Pneumonia
caused by infection often results in cough, chest pain, fever, and difficulty breathing.
X-rays
and examination of the sputum (phlegm) are often used to help diagnose
pneumonia, though some types may require more extensive testing. When pneumonia
is caused by infection, antibiotic medication is typically used. There are vaccines
which can prevent certain kinds of pneumonia.
Often,
pneumonia is the result of another medical illness, such as lung cancer
or alcohol
abuse. The outcome of each case depends on the type of pneumonia, the correct
treatment, and the underlying health of the individual.
Transmission of Influenza Viruses from
Animals to People
From the Centers for Disease Control and
Prevention (CDC)
Influenza A viruses are found in many different animals, including
ducks, chickens, pigs, whales, horses, and seals. Influenza B viruses circulate
widely only among humans.
Wild
birds are the primary natural reservoir for all subtypes of Influenza A viruses
and are thought to be the source of Influenza A viruses in all other animals.
Most influenza viruses cause asymptomatic (showing no symptoms) or mild
infection in birds; however, the range of symptoms in birds varies greatly
depending on the strain of virus.
Pigs can be infected with both human and avian (another name for birds)
influenza viruses in addition to swine influenza viruses. Infected pigs get
symptoms similar to humans, such as cough, fever, and runny nose. Because pigs
are susceptible to avian, human and swine influenza viruses, they potentially
may be infected with influenza viruses from different species (e.g., ducks and
humans) at the same time. If this happens, it is possible for the genes of
these viruses to mix and create a new virus. For example, if a pig were
infected with a human influenza virus and an avian influenza virus at the same
time, the viruses could mix and produce a new virus that had most of the genes
from the human virus, but a protein from the avian virus. The resulting new
virus would likely be able to infect humans and spread from person to person,
but it would have surface proteins not previously seen in influenza viruses
that infect humans. This type of major change in the Influenza A viruses is
known as antigenic
shift. Antigenic shift results when a new Influenza A subtype to
which most people have little or no immune protection infects humans. If this
new virus causes illness in people and can be transmitted easily from person to
person, an influenza pandemic can occur.
Influenza viruses can change in one other way. This is called antigenic drift.
These are small changes in the virus that happen continually over time.
Antigenic drift produces new virus strains that may not be recognized by the
body's immune system. This process works as follows: a person infected with a
particular flu virus strain develops antibody against that virus. As newer
virus strains appear, the antibodies against the older strains no longer
recognize the "newer" virus, and re-infection can occur. This is one
of the main reasons why people can get the flu more than one time. In most
years, one or two of the three virus strains in the influenza vaccine are
updated to keep up with the changes in the circulating flu viruses. So, people
who want to be protected from flu need to get a flu shot every year. While influenza viruses are changing by
antigenic drift all the time, antigenic shift happens only occasionally. Type A
viruses undergo both kinds of changes; Influenza Type B viruses change only by
the more gradual process of antigenic drift.