Cell culture and pathogen isolation
Serum samples were collected from 6 critically ill patients and inoculated into Vero and Bhk cells for routine culture and blind passage 3. Cell cultures were frozen-thawed once, nucleic acids were extracted and reverse transcribed for PCR detection. The amplified PCR products were subjected to agarose gel electrophoresis, and the positive products were sent to Sangon Bioengineering (Shanghai) Co., LTD for sequencing.