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بسم الله الرحمن الرحيم. Avian (Bird) Influenza... What You Need to Know. Dr.Tarek Mansour. 21,Nov, 2005. What is avian influenza (bird flu)?.

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بسم الله الرحمن الرحيم

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What is avian influenza (bird flu)?

Bird flu is an infection caused by avian (bird) influenza (flu) viruses. These flu viruses occur naturally among birds. Wild birds worldwide carry the viruses in their intestines, but usually do not get sick from them. However, bird flu is very contagious among birds and can make some domesticated birds, including chickens, ducks, and turkeys, very sick and kill them.


Do bird flu viruses infect humans?

Bird flu viruses do not usually infect humans, but more than 100 confirmed cases of human infection with bird flu viruses have occurred since 1997.


How is avian flu H5N1 transmitted from birds to humans?

Most of the people infected by H5N1 avian flu caught it from working closely with live infected birds. The virus is found in infected bird's droppings, saliva, etc.


Instances of Avian Influenza Infections in Humans

Confirmed instances of avian influenza viruses infecting humans since 1997 include:

1- H5N1, Hong Kong, Special Administrative Region, 1997: Highly pathogenic avian influenza A (H5N1) infections occurred in both poultry and humans. This was the first time an avian influenza A virus transmission directly from birds to humans had been found. During this outbreak, 18 people were hospitalized and six of them died.

2- H9N2, China and Hong Kong, Special Administrative Region, 1999: Low pathogenic avian influenza A (H9N2) virus infection was confirmed in two children and resulted in uncomplicated influenza-like illness. Both patients recovered.

3- H7N2, Virginia, 2002.


4- H5N1, China and Hong Kong, Special Administrative Region, 2003: Two cases of highly pathogenic avian influenza A (H5N1) infection occurred among members of a Hong Kong family that had traveled to China. One person recovered, the other died.

5- H7N7, Netherlands, 2003: In total, 89 people were confirmed to have H7N7 influenza virus infection associated with this poultry outbreak. There was one death among the 89 total cases.

6- H9N2, Hong Kong, Special Administrative Region, 2003: infection was confirmed in a child in Hong Kong. The child was hospitalized and recovered.

7- H7N2, New York, 2003: In November 2003.

8- H7N3 in Canada, 2004: In February 2004.

9- H5N1, Thailand and Vietnam, 2004.


Should I panic ????

No, not yet. But now would be a good time to learn more about viruses and flu so please enjoy my.


Types, Subtypes, and Strains

There are three types of influenza viruses: A, B, and C.


Influenza Type AInfluenza type A viruses can infect people, birds, pigs, horses, seals, whales, and other animals, but wild birds are the natural hosts for these viruses. Influenza type A viruses are divided into subtypes based on two proteins on the surface of the virus. These proteins are called hemagglutinin (HA) and neuraminidase (NA). Subtypes of influenza A virus are named according to their HA and NA surface proteins.

Influenza Type BInfluenza B viruses are normally found only in humans. Unlike influenza A viruses, these viruses are not classified according to subtype. Although influenza type B viruses can cause human epidemics, they have not caused pandemics.

Influenza Type CInfluenza type C viruses cause mild illness in humans and do not cause epidemics or pandemics. These viruses are not classified according to subtype.


How Influenza Viruses Change: Drift and Shift

- Influenza viruses can change in two different ways.

- One type is called "antigenic drift," which occurs through small changes in the virus that happen continually over time. Antigenic drift produces new virus strains that may not be recognized by antibodies to earlier influenza strains. 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. For this reason, people who want to be immunized against influenza need to receive a flu vaccination every year.


- The other type of change is called "antigenic shift." Antigenic shift is an abrupt, major change in the influenza A viruses, resulting in a new influenza virus that can infect humans and has a hemagglutinin protein or hemagglutinin and neuraminidase protein combination that has not been seen in humans for many years. Antigenic shift results in a new influenza A subtype.

- Influenza viruses are changing by antigenic drift all the time, but antigenic shift happens only occasionally. Influenza type A viruses undergo both kinds of changes; influenza type B viruses change only by the more gradual process of antigenic drift .


Symptoms of Avian Flu in Humans

The most common symptoms of avian influenza in humans are:



sore throat

muscle aches

eye infections



Complications of Avian Flu

Life threatening complications of avian flu are:

- Viral pneumonia

- Acute respiratory distress syndrome



1- Wild birds act as natural asymptomatic carrier.

2- One of the primary concerns is that the virus could quickly spread across countries as various birds follow their migration routes.

3- Most of the people infected by H5N1 avian flu caught it from working closely with live infected birds.

4- The severity of the infection will depend to large part on the state of the infected person immune system.


As a result of widespread use of antiviral drug amantadine as a preventive or treatment for chickens in Chine starting 1990s some strains of the avian flu virus have developed drug resistance against amantadine.