When reviewing a white blood cell (WBC) count, which element is typically elevated in a viral infection?

When reviewing a white blood cell (WBC) count, which element is typically elevated in a viral infection?

• A. Bands
• B. Leukocytes
• C. Lymphocytes
• D. Neutrophils

Answer: (C)

When a viral infection is present, the immune response is dominated by lymphocytes. Lymphocytes—primarily T cells that target infected cells and B cells that produce antibodies—proliferate in response to viruses, leading to an elevated absolute lymphocyte count and a higher proportion of lymphocytes on the differential. This pattern helps distinguish viral infections from bacterial ones, where neutrophils (and often bands, indicating a left shift) tend to rise. The total white count can be normal or elevated in viral infections, but the hallmark is the relative and often absolute increase in lymphocytes, sometimes with atypical lymphocytes in certain viruses like EBV or CMV.

When a viral infection is present, the immune response is dominated by lymphocytes. Lymphocytes—primarily T cells that target infected cells and B cells that produce antibodies—proliferate in response to viruses, leading to an elevated absolute lymphocyte count and a higher proportion of lymphocytes on the differential. This pattern helps distinguish viral infections from bacterial ones, where neutrophils (and often bands, indicating a left shift) tend to rise. The total white count can be normal or elevated in viral infections, but the hallmark is the relative and often absolute increase in lymphocytes, sometimes with atypical lymphocytes in certain viruses like EBV or CMV.