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Understand
In order to understand the risks associated with a possible flu pandemic, it is important to recognize the four (4) primary types of flu and understand how they differ from each other.
Seasonal Flu, Swine Flu, Avian Flu, Pandemic Flu
(The below information is adapted from material gathered from the Centers for Disease Control, www.cdc.gov/flu .)
Seasonal Flu
Seasonal flu is a contagious respiratory illness caused by influenza viruses that can cause mild to severe symptoms and can sometimes lead to death, generally in the elderly or people with underlying chronic illnesses. Getting a flu vaccination each fall is the best way to prevent this illness.
During an average year in the United States:
- 5 to 20 percent of the population gets the flu
- over 200,000 people are hospitalized from flu complications
- about 36,000 people die
How Flu Spreads
Flu viruses spread in respiratory droplets caused by coughing and sneezing. They usually spread from person to person, through touching something with flu viruses on it and then touching their mouth or nose sometimes infects people. Most healthy adults are infectious beginning one day before symptoms develop and up to five days after becoming sick. That means you can give someone else the flu before you know you are sick, as well as while you are sick.
Common Flu Symptoms
- fever (usually high, greater than 100.5º Fahrenheit)
- headache
- extreme fatigue
- dry cough
- sore throat
- runny or stuffy nose
- muscle aches
- occasionally stomach symptoms, such as nausea, vomiting, and diarrhea (more common in children than adults)
Certain groups—such as older people, young children, and people with certain health conditions—are at a higher risk for serious flu complications.
Flu Complications
Complications of flu can include bacterial pneumonia, dehydration, and worsening of chronic medical conditions like congestive heart failure, asthma, or diabetes. Children may get sinus problems and ear infections.
H1N1 (Swine) Flu
H1N1 Influenza (swine flu) is a respiratory disease of pigs caused by type A influenza viruses that causes regular outbreaks in pigs. People do not normally get swine flu, but human infections can and do happen. Swine flu viruses have been reported to spread from person-to-person, but in the past, this transmission was limited and not sustained beyond three people.
Are there human infections with swine flu in the U.S.?
In late March and early April 2009, cases of human infection with swine influenza A (H1N1) viruses were first reported in Southern California and near San Antonio, Texas. Other U.S. states have reported cases of H1N1 flu infection in humans and cases have been reported internationally as well. An updated case count of confirmed H1N1 flu infections in the United States is kept at http://www.cdc.gov/swineflu/investigation.htm CDC and local and state health agencies are working together to investigate this situation.
Is this H1N1 flu virus contagious?
CDC has determined that this swine influenza A (H1N1) virus is contagious and is spreading from human to human. However, at this time, it is not known how easily the virus spreads between people.
What are the signs and symptoms of swine flu in people?
The symptoms of H1N1 flu in people are similar to the symptoms of regular human flu and include fever, cough, sore throat, body aches, headache, chills and fatigue. Some people have reported diarrhea and vomiting associated with swine flu. In the past, severe illness (pneumonia and respiratory failure) and deaths have been reported with swine flu infection in people. Like seasonal flu, H1N1 flu may cause a worsening of underlying chronic medical conditions.
How does H1N1 flu spread?
Spread of this swine influenza A (H1N1) virus is thought to be happening in the same way that seasonal flu spreads. Flu viruses are spread mainly from person to person through coughing or sneezing of people with influenza. Sometimes people may become infected by touching something with flu viruses on it and then touching their mouth or nose.
Avian “Bird” Flu
Avian (or bird) flu is caused by influenza viruses that occur naturally among wild birds. The H5N1 variant, one strain of the bird flu, is deadly to domestic fowl and can be transmitted from birds to humans, though the risk is generally low to most people. Several species of wild fowl can harbor this virus without showing signs of illness. Confirmed cases of avian flu infection in humans have been reported since 1997, and the H5N1 flu in humans can currently be found in much of Asia and has spread to Europe. There is no human immunity and no vaccine is available, however vaccine development efforts are underway.
Avian H5N1 flu in humans is currently very limited and NOT a pandemic. However, it is uncertain whether the currently circulating H5N1 virus will lead to a global disease outbreak in humans.
See www.pandemicflu.gov/#map for a map showing the nations with confirmed human cases and the number of cases.
How the Bird Flu Spreads
Close contact with infected poultry has been the primary source for human infection. Wild birds can carry the viruses without showing signs of illness, and may also be infectious to humans. The virus is quite contagious in birds, though the H5N1 virus does not infect humans easily. Close contact with sick domestic fowl or consumption of uncooked or undercooked poultry has been the usual cause of illness when people have become infected.
The spread of avian influenza viruses from one ill person to another has been reported very rarely, and transmission has not been observed to continue beyond one person. Because all influenza viruses have the ability to change, scientists are concerned that the H5N1 virus could one day easily infect humans and spread easily from one person to another.
More than half of the humans who have sought health care because of H5N1 infections with bird flu have died. It is unclear how many people have been infected but have not developed severe symptoms.
Symptoms of Bird Flu
Symptoms of bird flu in humans are typical human influenza-like symptoms (e.g., fever, cough, sore throat, and muscle aches). In addition, bird flu-specific symptoms include eye infections, pneumonia, severe respiratory diseases (such as acute respiratory distress), and other severe and life-threatening complications. Some of the symptoms are a consequence of the body's response to this particular virus.
Pandemic Flu
A pandemic is a global disease outbreak. A flu pandemic occurs when a new influenza virus emerges for which people have little or no immunity, and for which there is no vaccine. A pandemic disease spreads easily from person to person, causes serious illness, and can sweep across the country and around the world in a very short time.
Impact of a Pandemic
A pandemic may come and go in waves, each of which can last for six to eight weeks.
An especially severe influenza pandemic could lead to high levels of illness, death, social disruption, and economic loss. Everyday life would be disrupted because so many people in so many places become seriously ill at the same time. Impacts can range from school and business closings to the interruption of basic services such as public transportation and food delivery.
Health care facilities can be overwhelmed, creating a shortage of hospital staff, beds, ventilators and other supplies. The need for vaccine is likely to outstrip supply, and the supply of antiviral drugs also is likely to be inadequate early in a pandemic. Difficult decisions will need to be made regarding who gets antiviral drugs and vaccines.
Historically, the 20th century experienced three influenza pandemics:
- 1918 influenza pandemic caused at least 675,000 U.S. deaths and up to 50 million deaths worldwide
- 1957 influenza pandemic caused at least 70,000 U.S. deaths and 1-2 million deaths worldwide
- 1968 influenza pandemic caused about 34,000 U.S. deaths and 700,000 deaths worldwide
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