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Influenza
Health Guide
What Is Influenza (Flu) And How Is It Caused?

Influenza is a contagious disease caused by a virus that infects many parts of the body, including the lungs. As a disease, it is very unpredictable - here in New Zealand, sporadic outbreaks happen from year to year, with small incidences some years and epidemics in other years.

When someone who has influenza sneezes, coughs, or even talks, the influenza virus is expelled into the air and may be inhaled by anyone close by. Influenza may also be transmitted by direct hand contact.

What Happens When You Get Influenza?
Influenza works rapidly and after infection it only takes 24-72 for the symptoms to take hold.
When influenza strikes the lungs, the lining of the respiratory tract is damaged. The tissues become swollen and inflamed. Fortunately, the damage is rarely permanent. The tissues usually heal within a few weeks.

Influenza is often called a respiratory disease, but it affects the whole body. The victim usually becomes acutely ill with fever, chills, weakness, loss of appetite and aching of the head, back, arms and legs. The influenza sufferer may also have a sore throat and a dry cough, nausea, and burning eyes.

The fever mounts quickly; temperature may rise to 40 degrees Celcius but after two or three days, it usually subsides. The patient is often left exhausted for days afterwards.

Is Influenza Considered Serious?

For healthy children and adults, influenza is typically a moderately severe illness. Most people are back on their feet within a week.

For people who are not healthy or well to begin with (people who suffer from long term illness or people whose resistence is weakened due to age), influenza can be very severe and even fatal. The symptoms described above have a greater impact on these persons. In addition, complications can occur.

Most of these complications are bacterial infections because the body can be so weakened by influenza that its defenses against bacteria are low. Bacterial pneumonia is the most common complication of influenza. But the sinuses and inner ears may become inflamed and painful.

Who Gets Influenza?

Anyone can get influenza, especially when it is widespread in the community. People who are not healthy or well to begin with are particularly susceptible to the complications that can follow. These people are known as "high risk" and should be immunized.

For anyone at high risk, influenza is a very serious illness. You may be at high risk if you:

  • Have chronic lung disease such as asthma, emphysema, chronic bronchitis, bronchiectasis, tuberculosis, or cystic fibrosis.
  • Have heart disease.
  • Have chronic kidney disease.
  • Have diabetes or another chronic metabolic disorder.
  • Have severe anemia.
  • Have diseases or are having treatments that depress immunity.
  • Are residing in a nursing home or other chronic care facility.
  • Are over 65 years of age.

A doctor, nurse, or other provider of care to high-risk persons should be immunized to protect high-risk patients.

How Are Influenza And Complications Prevented?
The WHO Influenza Reference Centre monitors the occurence of the disease within the country and overseas. Vaccination has a high degree of success against influenza infection. A new vaccine is made each year so that the vaccine can contain influenza viruses that are expected to cause illness that year.

The viruses in the vaccine are inactivated so that someone vaccinated cannot get influenza from the vaccine. Instead the person vaccinated develops protection in his or her body in the form of substances called antibodies.

The amount of antibodies in the body is greatest 1 or 2 months after vaccination and then gradually declines. For that reason and because the influenza viruses usually change each year, a high-risk person should be vaccinated each fall with the

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