The goal of this observational study is to describe the immune signature of acute pulmonary infection.The main questions it aims to answer are:

1. Nasal mucosal immune response in patients with influenza infection
2. Difference of immune response between Viral sepsis and Bacterial sepsis
3. Immunological differences between Viral sepsis and Viral pneumonia

1. Aging could influence host immune response. Elderly people are more likely to progress to severe pneumonia than young people. Nasal mucosa is the initial infection site of influenza infection. Single cell sequencing of nasal mucosal cell that may provide valuable insights into host response to influenza infection.
2. Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection. Although bacteria are considered as the main pathgens of sepsis，SARS-CoV-2 or influenza infection also can cause multiple organ dysfunction which meet the definition of Sepsis 3.0. Viral sepsis has not received enough attention for a long time. It is important to understand the difference between viral sepsis and bacterial sepsis that may help to develop better strategies to diagnose and treat sepsis.
3. Viral pneumonia is one of the leading infectious cause of death woldwide.Pneumina is the most common cause of sepsis.The mechanism of viral pneumonia progressing to sepsis needs to be further investigated.

Inclusion Criteria:

1. Age ≥18 years at time of signing Informed Consent Form
2. chest imaging confirmed pneumonia.
3. Informed consent is obtained
4. The pneumonia onset ≤8 days

Exclusion Criteria:

1. SaO2/SPO2≤94% on room air or Pa02/Fi02 ratio <300mgHg before the onset of pneumonia
2. Severe liver disease (e.g. Child Pugh score ≥ C, AST>5 times upper limit)
3. Patients with known severe renal impairment (estimated glomerular filtration rate ≤30 mL/min/1.73 m2) or receiving continuous renal replacement therapy, hemodialysis,peritoneal dialysis）
4. Pregnant Or Lactating Women
5. Patients were eligible for organ transplantation or had undergone previous organ transplantation surgery
6. HIV infection
7. Had unstable angina or myocardial infarction within 30 days without vascular recanalization treatment

Patients who are diagnosed pneumonia and signed informed consent will be enrolled.

We will share the transcriptome data with other researchers.