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what is influenza?

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  • what is influenza?

    hiiiiiii every body
    انا كتبت هل موضوع بمساعده الاخ عوني يوسف
    الدكتوره في الجامعه كتير عجبها الموضوع
    انشالله يعجبكم انتو كمان و تستفيدو منو........


    What is influenza?

    Influenza, commonly called "the flu," is an illness caused by viruses that infect the respiratory tract. Compared with most other viral respiratory infections, such as the common cold, influenza (flu) infection often causes a more severe illness with a mortality rate (death rate) of about 0.1% of people who are infected with the virus. Unusually severe worldwide outbreaks (pandemics) have occurred several times in the last 100 years since influenza virus was identified in 1933. By an examination of preserved tissue, the worst influenza pandemic occurred in 1918 when the virus caused between 40 to 100 million deaths with a mortality rate estimated to range from 2% to 20%.

    Haemophilus influenzae is a bacterium that was incorrectly considered to cause the flu until the virus was demonstrated to be the correct cause in 1933. This bacterium can cause lung infections in infants and children, and it occasionally causes ear, eye, sinus, joint, and a few other infections, but not the flu.



    What are the causes of the flu?

    The flu (influenza) viruses

    Influenza viruses are divided into three types, designated A, B, and C. Influenza types A and B are responsible for epidemics of respiratory illness that occur almost every winter and are often associated with increased rates of hospitalization and death. Influenza type C differs from types A and B in some important ways. Type C infection usually causes either a very mild respiratory illness or no symptoms at all; it does not cause epidemics and does not have the severe public health impact of influenza types A and B. Efforts to control the impact of influenza are aimed at types A and B, and the remainder of this discussion will be devoted only to these two types.

    Influenza viruses continually change over time, usually by mutation (change in the viral RNA). This constant changing often enables the virus to evade the immune system of the host (humans, birds, and other animals) so that the host is susceptible to changing influenza virus infections throughout life. This process works as follows: a host infected with influenza virus develops antibody against that virus; as the virus changes, the "first" antibody no longer recognizes the "newer" virus and reinfection can occur. The first antibody may in some instances provide partial protection against reinfection with an influenza virus.

    Type A viruses are divided into types based on differences in two viral surface proteins called the hemagglutinin (H) and the neuraminidase (N). There are 16 known H subtypes and nine known N subtypes. These surface proteins can occur in many combinations. When spread by droplets or direct contact, the virus, if not killed by the host's immune system, replicates in the respiratory tract and damages host cells.


    Antigenic shift and drift

    Influenza type A viruses undergo two kinds of changes. One is a series of mutations that occurs over time and causes a gradual evolution of the virus. This is called antigenic "drift." The other kind of change is an abrupt change in the hemagglutinin and/or the neuraminidase proteins. This is called antigenic "shift." In this case, a new subtype of the virus suddenly emerges. Type A viruses undergo both kinds of changes; influenza type B viruses change only by the more gradual process of antigenic drift and therefore do not cause pandemics.

    Never say to God I have a big problem
    say to problem I have a big God

    :sm173:

  • #2
    coooooool
    thank you
    http://up1.m5zn.com/photo/2009/1/24/...36kx6u.jpg/jpg

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    • #3
      :sm202::sm202:الله يعطيك العافيه

      صراحه شكلي بستفيد منك

      تعليق


      • #4
        شكرا لك أختي الكريمة
        تحياتي لك
        عيادة الدكتور أحمد بكور لطب الأطفال
        أهم مواضيع عيادة الدكتور أحمد بكور لطب الأطفال

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        • #5
          thank you every body
          :sm170::sm170::sm170::sm170::sm170::sm170::sm170:: sm170::sm170::sm170:
          Never say to God I have a big problem
          say to problem I have a big God

          :sm173:

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          • #6
            رااائع اختي الموضوع

            جزيل الشكر لك وللاخ عوني يوسف ولمجهودكم الراائع

            مودتي وتقديري لكم

            تعليق


            • #7
              المشاركة الأصلية بواسطة لولة البايو مشاهدة المشاركة
              رااائع اختي الموضوع

              جزيل الشكر لك وللاخ عوني يوسف ولمجهودكم الراائع

              مودتي وتقديري لكم
              احقاقا للحق اضافاتى على الموضوع بسيطة ولكن الجهد الاكبر كان ل misslove
              شكرا للجميع
              http://www.facebook.com/MkhtbrAlshjayt?ref=hl

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              • #8
                thanks for every body
                Never say to God I have a big problem
                say to problem I have a big God

                :sm173:

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                • #9
                  جزاكي الله خيرا
                  شكرا جزيلا

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                  • #10
                    موضوع جميل

                    شكراً لك والأخ عوني

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                    • #11
                      [B]موضوع جميل اختي بس لوكان تطرقتي الى lab dignosis يكون افضل . على العموم جهد تشكرين عليه.

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