Acute nephritis is not contagious. Although acute nephritis often follows a history of streptococcal infection, when such streptococci infect the human body, they can cause an immune complex reaction, which circulates through the bloodstream to the kidneys causing inflammation. Furthermore, these streptococci can have a cross-immune reaction with kidney tissue. These mechanisms together lead to diffuse proliferation of glomerular capillary cells, causing hematuria, proteinuria, and even renal failure. However, this condition generally is not contagious. Although this disease is related to streptococcal infection, these streptococci are mostly opportunistic pathogens and are unlikely to cause harm to people other than the patient, making it difficult to trigger a nephritis reaction again.