1. hospital staff with serious underlying diseases; 2. pregnant and lactating women; 3. long-term vegetarians; 4. long-term chronic diarrhea, history of subtotal gastrectomy, biliary obstructive disease and pancreatic disease.

1. hospital staff with serious underlying diseases; 2. pregnant and lactating women; 3. long-term vegetarians; 4. long-term chronic diarrhea, history of subtotal gastrectomy, biliary obstructive disease and pancreatic disease.

hospital staff with serious underlying diseases; pregnant and lactating women; long-term vegetarians; long-term chronic diarrhea, history of subtotal gastrectomy, biliary obstructive disease and pancreatic disease.

hospital staff with serious underlying diseases; pregnant and lactating women; long-term vegetarians; long-term chronic diarrhea, history of subtotal gastrectomy, biliary obstructive disease and pancreatic disease.