A Multi-center Study to Determine the Prevalence and Influence of Pertussis on Subacute Cough in Shenzhen

1. Investigate the incidence and epidemiological characteristics of pertussis infection in subaute cough population.
2. To explore the relationship between pertussis infection and subaute cough.

• Blood sample (Procedure): 2 ml venous blood was collected and separated into serum.
• Data collection (Procedure): 1. Whether the patient has been vaccinated with DPT vaccine and record the time of vaccination; 2. Medication situation of patients in the past year, including rescue drugs, antitussive and expectorant drugs, inhaled corticosteroids and antibiotics;
• Throat swab (Procedure): Before the collection of oropharyngeal swabs, instruct the patient to wash the mouth or gargle, fix the patient's head, open the mouth and expose the throat. If necessary, use a tongue depressor to gently press the tongue. Use the swab to wipe the secretion on both sides of the palatal arch, pharynx and tonsil with a sensitive and gentle action, and quickly withdraw the swab to avoid contacting other parts of the mouth. Put the swab in the sterile test tube, plug the opening with cotton ball, and send it for inspection and registration in time.

Primary outcomes

• Evaluation of the prevalence of pertussis among subacute cough [Day 0 of each subject at the time of enrollment.]: According to the positive rate of bordetella pertussis nucleic acid, evaluate the prevalence of pertussis in subaute cough.
• Evaluation of the correlation between pertussis and subacute cough [Day 0 of each subject at the time of enrollment.]: Evaluate the correlation between pertussis infection and subacute cough by pertussis positive rate and clinical parameters.

Secondary outcomes

• Evaluation of the seroprevalence of bordetella pertussis in subacute cough [Day 0 of each subject at the time of enrollment.]: According to anti-pertussis (anti-PT) antibody levels, assess the overall seroprevalence of bordetella pertussis in subacute cough.
• Evaluation of the cut-off value for serological diagnosis of pertussis. [Day 0 of each subject at the time of enrollment.]: By comparing the nucleic acid and antibody levels of Bordetella pertussis to evaluate the antibody cut-off value for serological diagnosis of pertussis.
• Evaluation of the subtype of bordetella pertussis. [Day 0 of each subject at the time of enrollment.]: According to the level and pattern of different anti-pertussis antibodies (anti-PT, anti-FHA, anti-PRN, anti-FIM2, anti-FIM3), assess the subtype of Bordetella pertussis.

Sex: All, ages: 40 Years to 80 Years

Inclusion Criteria:

* The cough lasts 3 to 8 weeks and there is no obvious evidence of lung disease on chest X-ray.

Exclusion Criteria:

* 1\. Major diseases except subaute cough; 2. Significant abnormality in laboratory examination; 3. Clinical diagnosis of lung cancer, bronchiectasis, pneumoconiosis or other simple restrictive ventilation dysfunction; 4. Patients with a history of asthma, allergic rhinitis, or a blood eosinophil count of 2600/mm3 (0.6x10\^9/L) within 4 weeks; 5. Currently suffering from active tuberculosis; 6. Patients with life-threatening pulmonary embolism, or al-antitrypsin deficiency, or cystic fibrosis; 7. Patients who have undergone lung resection.

• Lingwei Wang, Study director, Shenzhen People's Hospital