This is a prospective cohort study using gene expression to study patients with infection and sepsis from pneumonia.

This is a prospective cohort study using single cell transcriptomic profiling and plasma DNA tissue mapping on patients with pneumonia with or without sepsis. The major application of the investigator's study would be the discovery of gene expressions in different leucocytes and plasma DNA associated with each type of organ dysfunction in sepsis. These include cardiovascular, respiratory, hepatic, renal, neurological and haematological dysfunction. This would help prediction, diagnosis and development of therapies to treat sepsis. Leucocyte single cell transcriptome and plasma DNA tissue mapping may addresses the limitations of current evidence in 3 ways: (1) differentiate patients with uncomplicated pneumonia versus pneumonia with associated sepsis, (2) correlation with types and severity of organ dysfunction and (3) identifying molecular phenotypes of sepsis.

Inclusion Criteria:

All of the following:

• newly admitted adult patients (≥ 18 years old)
• suspected community acquired pneumonia (CAP)
• compatible history of either sputum or cough or fever or rigors within 1 week
• chest X-ray infiltrates

Exclusion Criteria:

Any of the following:

• chest symptoms not solely accounted by pneumonia (cardiac failure, non cardiogenic pulmonary oedema, suspected pulmonary embolism, suspected secondary acute respiratory distress syndrome)
• immunosuppression
• current malignancy
• blood samples for gene expression could not be taken within 24 hours of admission
• prisoner/cogni tive impairment
• blood transfusion within 1 month
• hospitalization within 1 month

All adult patients admitted with community acquired pneumonia to a tertiary hospital in Hong Kong.