Why does the white blood cell (WBC) count go below normal with a viral infection?

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I've read the a bacterial infection can cause high WBC count, but a viral infection can cause a low WBC count. Why does the WBC go lower with a virus, but go higher with a ...show more
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Well, maybe. You can actually see both high and low WBC counts with bacterial AND viral infections.

So why can the WBC count go below normal with a viral infection? First you have to try to determine WHY the WBC count is low. For example, a low white blood cell count can be the result of a prior infection - too many WBCs have been called into action and have been used up. This makes an individual more susceptible to outside infections like viruses. So when a blood test is performed, the WBC will be low, and the person will have a secondary viral infection going on.

However, there are viruses that can lower the number of a particular type of white blood cell. For example, with neutropenia, certain viruses (e.g. Hepatitis B virus) can decrease the production of neutrophils. So, you may see a below normal neutrophil count in a viral infection.

The cautionary tale is this - viral and bacterial infections can BOTH raise/lower WBC counts. Leukopenia can be seen in some viral infections (HIV) or severe bacterial infections. Leukocytosis can be seen in some viral infections (infectious mononucleosis) or bacterial infections.

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5 out of 5
Excellent answer, thank you!
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Other Answers (1)

  • Stephanie answered 6 years ago
    Granulocytes (polymorphonuclear leucocytes): leukocytes characterised by the presence of differently staining granules in their cytoplasm when viewed under light microscopy. These granules are membrane-bound enzymes which primarily act in the digestion of endocytosed particles. There are three types of granulocytes: neutrophils, basophils, and eosinophils, which are named according to their staining properties.
    Agranulocytes (mononuclear leucocytes): leukocytes characterized by the apparent absence of granules in their cytoplasm. Although the name implies a lack of granules these cells do contain non-specific azurophilic granules, which are lysosomes [2]. The cells include lymphocytes, monocytes, and macrophages.

    Depending on the illness some "cytes" will either increase or decrease.

    An excellent article can be found by going to http://en.wikipedia.org/wiki/White_blood...


    had a chronic illness, hcv which cause a rise in my wbc
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