To increase the sensitivity and specificity of detecting high-pathogenic avian influenza variant (HSN1), laboratory studies were conducted at low virus concentrations in water samples, by using magnetic immunosorbent (MIS) test systems and selective avian influenza virus concentrating units. MIS-based selective virus concentrating, followed by rapid assays (ELIZA and RT-PCR), detect the low concentrations (as low as 10 nm in 5,000 ml of water) of avian influenza A/H5N1 antigen and RNA. The method developed opens new avenues for indication of an avian influenza pathogen in different environmental objects, including the water of surface water reservoirs of unlimited volume, with varying pollutions and low virus concentrations.