* the nucleic acid test result of novel coronavirus has always been negative after entering the fang chang hospital. * patients who have history of nasal surgery, or current use of nasal saline irrigation or other intranasal medications. * patients with thyroid diseases , respiratory diseases or other serious basic diseases. * allergy to iodine. * participation in another prospective covid related research project(clinical trial). * pregnancy or lactation * patients with immune deficiency (such as patients with malignant tumors, organ or bone marrow transplantation, patients with aids, and those taking immunosuppressive drugs within 3 months before screening). * other patients considered unsuitable by the investigator to participate in this study

* the nucleic acid test result of novel coronavirus has always been negative after entering the fang chang hospital. * patients who have history of nasal surgery, or current use of nasal saline irrigation or other intranasal medications. * patients with thyroid diseases , respiratory diseases or other serious basic diseases. * allergy to iodine. * participation in another prospective covid related research project(clinical trial). * pregnancy or lactation * patients with immune deficiency (such as patients with malignant tumors, organ or bone marrow transplantation, patients with aids, and those taking immunosuppressive drugs within 3 months before screening). * other patients considered unsuitable by the investigator to participate in this study

the nucleic acid test result of novel coronavirus has always been negative after entering the fang chang hospital. patients who have history of nasal surgery, or current use of nasal saline irrigation or other intranasal medications. patients with thyroid diseases , respiratory diseases or other serious basic diseases. allergy to iodine. participation in another prospective covid related research project(clinical trial). pregnancy or lactation patients with immune deficiency (such as patients with malignant tumors, organ or bone marrow transplantation, patients with aids, and those taking immunosuppressive drugs within 3 months before screening). other patients considered unsuitable by the investigator to participate in this study

the nucleic acid test result of novel coronavirus has always been negative after entering the fang chang hospital. patients who have history of nasal surgery, or current use of nasal saline irrigation or other intranasal medications. patients with thyroid diseases , respiratory diseases or other serious basic diseases. allergy to iodine. participation in another prospective covid related research project(clinical trial). pregnancy or lactation patients with immune deficiency (such as patients with malignant tumors, organ or bone marrow transplantation, patients with aids, and those taking immunosuppressive drugs within 3 months before screening). other patients considered unsuitable by the investigator to participate in this study