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How do fever and a high white blood cell count signal disease?

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Health monitoring — human disease The routine monitoring of blood pressure levels is an important part of assessing an individual's health. Blood pressure provides information about the amount of blood in circulation and about heart function and thus is an important indicator of disease.

Fever and an elevated white blood cell count (leukocytosis) are key components of the body's immune system response to disease, particularly infections.12

Fever as a Defense Mechanism

Fever is a defensive reaction triggered when bacteria or viruses cause tissue injury. The immune system produces pyrogens, which travel to the hypothalamus in the brain and reset the body's temperature higher. This elevated temperature helps the body by:2
* Stimulating the activity, motion, and multiplication of white blood cells.2
* Increasing the production of antibodies.2
* Directly inhibiting or killing certain microorganisms that cannot tolerate higher temperatures.2

Leukocytosis and Disease

Leukocytosis is an abnormal increase in the number of white blood cells, often occurring in response to infection. As the body detects pathogens, it demands more white cells from the bone marrow to fight the invader. Different types of infections trigger specific increases in white cell types, such as neutrophils for bacterial infections or lymphocytes for viral origins. These counts typically return to normal as the infection subsides.13