Blood Infection

"You have a blood infection", has become an everyday phrase.

And it's very difficult to then explain to the patient that "circulating blood does not get infected". A river does not get infected, a pond does.

If there are pathogens in the blood (viruses - viremia, bacteria - bacteremia, fungi - fungemia, etc.), it doesn't mean that the blood is infected, it is performing its main duty: Transport. If a pathogen has entered the blood (has passed the protective limiting barriers), it needs to reach the target areas where it finds the necessary environment to stay, feed, and multiply, and there it causes the corresponding structural and functional damage.

If in the peripheral blood analysis, there is an increase in leukocytes, neutrophils, precursors of neutrophils (bands, metamyelocytes, etc.), an increase in erythrocyte sedimentation rate (often accompanied by fever, etc.), it doesn't mean you have a "blood infection".

The blood's duty is to transport:

1. Erythrocytes and along with them hemoglobin and oxygen. For itself, the blood does not need erythrocytes, hemoglobin, or oxygen (erythrocytes secure the necessary energy through anaerobic glycolysis so as not to use up the oxygen for other cells).


2. Leukocytes (neutrophils, eosinophils, lymphocytes, bands, monocytes, etc.). For itself, the blood does not need leukocytes at all, they are produced in the Red Bone Marrow (lymphocytes also outside of it) and through the peripheral blood they are transported where they need to perform their duties, which are always outside the blood vessel.
   
   If a pathogen has reached the Basic Substance of the Connective Tissue, the first to arrive there should be neutrophils to eliminate it, and by performing their duty outside the blood vessel, these cells also die. To ensure a sufficient number of neutrophils enough for the elimination of the last pathogen (not a single pathogen should remain inside the body), the body uses reserves, increases production and when it cannot reach a sufficient number of mature cells (neutrophils), it releases their precursors, which are not fully effective (new soldiers), but can fight (bands, metamyelocytes).
   
   If the pathogen reaches the blood, there is another "warrior" that eliminates it directly - the spleen with the largest Mononuclear Phagocyte System in the body. And if the Non-Specific defense does not eliminate it, the Specific defense will come (Lymphocytes) and only if all these protective links are overcome (or are damaged) and the pathogen is not eliminated, it will reach its target areas, settle, feed, multiply with the corresponding local and systemic damages.


3. Platelets are the only formed element of the blood that the blood needs for itself and thus for all other cells of the body. Their duty is to ensure the stability of the small blood vessels (capillaries) and even more so they are needed only when the vessel wall is damaged, with the aim of stopping hemorrhage, i.e., the loss of blood with the corresponding consequences.


4. Of course, it transports hormones, lipids, amino acids, heat, etc. It also carries pathogens, tumor cells, etc.