the invention is directed to a treatment of diseases that are accompanied by quantitative and / or qualitative changes of blood extracellular dna and , more particularly , to a treatment of systemic bacterial , fungal and protozoan infections . the inventive method comprises introducing a treatment agent into a circulating blood system of a patient diagnosed with systemic infection caused by bacteria , fungi or protozoa , wherein said treatment agent destroys extracellular dna in said blood of said patient and wherein said treatment agent used to destroy said extracellular dna is a dnase enzyme : said agent being administered in doses and regimens which are sufficient to decrease the average molecular weight of circulating extracellular blood dna in the blood of said patient ; such decrease in the average molecular weight can be measured by gel electrophoresis of extracellular blood dna fraction from the blood of said patient . a dnase enzyme may be applied in a dose and regimen that provide a dnase dna hydrolytic activity measured in blood plasma that exceeds 1 . 5 kunitz units per 1 ml of blood plasma for more than 12 hours within a period of 24 hours .