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Why can viral infections affect the lymphocyte count?

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blood analysis The physical and chemical properties of a sample of blood are examined during blood analysis. The examination of blood is important for the accurate diagnosis of disease.

Viral infections frequently alter lymphocyte counts because these white blood cells are central to the body's immune response against viruses.12

When a virus enters the body, lymphocytes recognize viral antigens and multiply into clones to neutralize the threat. This often leads to lymphocytosis, an increase in the number of lymphocytes in the blood, which is a common characteristic of many viral infections. For instance, in infectious mononucleosis, the body produces atypical, enlarged lymphocytes as part of its defense mechanism.123

Conversely, some viral infections can cause a decrease in lymphocyte counts, known as lymphocytopenia. This occurs because certain viruses, such as HIV, selectively infect and destroy specific lymphocyte populations, such as helper T cells. Additionally, during some infections, the immune system may temporarily attack its own infected cells, or the virus may cause transient damage to the cells, leading to a temporary reduction in functional lymphocyte levels.14