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Influenza 2005, Now A Bird Flu Too?

Armen Hareyan's picture

Bird Flu - Influenza

It's always something with the flu. Last year, just when it seemed most people were beginning to accept the need for flu vaccine, there was a problem with one manufacturer, and there was not enough of the vaccine early in the season. Now, there's news coverage on avian flu in southeast Asia and many people are confused and afraid of the implications for those in the United States. It can be intimidating to sort it all out.

Influenza is caused by a group of viruses and is divided into three large categories: types A, B and C. Type C is not a significant problem. Type B is usually not as severe as type A which can be fatal in those with other health problems, such as heart or lung diseases, diabetes and weakened immune systems, and in small children and those older than 65.

Different proteins in the structure of the influenza viruses are attacked by the immune system and these proteins are used to define the type of flu virus. Not all flu virus types can infect humans -- some infect only animals, such as pigs or birds, and some infect across species. From year to year as many trillions of flu viruses reproduce worldwide, the proteins undergo slight variations. This is why new flu vaccines must be developed each year. The immune system must be ready to respond to the changed virus before the person is infected.

In influenza A, the two most important proteins, neuraminidase (N) and hemaglutinin (H), determine the major types of influenza. Influenza A viruses have one of 15 types of N and nine types of H proteins. For many years, the most important type A flu in the United States has been one or another version of H3N2 or H1N1.

One big difference between influenza type A and type B is that type A can cross species. It is thought that if two types of influenza A infect an animal at the same time, they can exchange genetic material during virus multiplication and become new major types. Type B does not cross species, so it does not do this.

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Manufacturers expect there to be a sufficient supply of vaccine to immunize everyone who needs or wants it this year. However, to assure that high-risk people are immunized should something happen to cause a shortage again this year, the Centers for Disease Control are recommending high-risk individuals be vaccinated first during October and everyone else later. Since influenza does not typically arrive until December, and it takes about two weeks to develop immunity, that should be plenty of time.

Those who should be vaccinated in October in order of priority include: individuals age 65 and older, particularly those with other medical problems; residents of long-term care facilities; individuals between the ages of two and 64 with medical problems that increase risk; individuals older than 65 who are otherwise healthy; all healthy children between 6 months and 2 years of age; pregnant women; health-care personnel in direct patient care; household contacts and caregivers of children younger than 6 months of age. The nasal spray version of the vaccine may be used for any healthy person from age 5 to 49 (who is not pregnant) without any priority on who should get it first.

There are medications that can shorten the course of the flu if started early in its course. The most effective medications are oseltamivir and zanamivir, which are available by prescription. These are also useful for individuals who have not been immunized who are exposed to influenza, to reduce the risk of contracting the disease.

In recent months there has been more news coverage on avian flu. As the name implies, this is a form of influenza that typically infects birds. It is an H5N1 type A flu, and the concern is that it is capable of spreading to humans who are exposed to infected birds, typically farmers and handlers of bird carcasses. There may have been a couple of cases of human-to-human spread, but they are so far very rare. The big concern is that if an animal such as a pig gets infected with a bird strain and a human strain at the same time, the two will mix up in a way that allows it to spread easily from human to human causing a worldwide pandemic like the Spanish flu of the early 20th century.

This is a major concern for physicians and researchers, but there is good news. A vaccine is being tested against this avian flu that so far appears to work as well as other flu vaccines. Also, the same antiviral drugs that work against other strains of influenza can treat avian flu. There is discussion on stockpiling enough antiviral medication to treat anyone infected should an epidemic occur.

So, for now, the avian flu is not the immediate concern. This year those in high-risk groups should begin getting their flu shots now. By November, anyone who wants to reduce the risk of getting the flu should get a flu shot. The only people who should not get a flu shot are those who are so sensitive to eggs, they stop breathing. The vaccine will not cause the flu, because the virus is dead in the injectable form. Sometimes the very first time a person ever receives the flu vaccine, they feel a bit like they are getting the flu because it works by tricking the immune system into thinking there is an infection. Subsequent years are generally well-tolerated.

Don't wait until the flu hits to get protection. It may not be the avian flu, but it's still the flu and as usual, an ounce of prevention is worth a pound of cure.