This project is a cross-sectional study. Investigators plan to search and collect 1600 publicly published fecal metagenomic and metatranscriptome data through the Pubmed database, by summarizing and analyzing them to construct an enterovirus database. 200 apparently healthy individuals are planned to be enrolled. At the time of enrollment, fecal specimens of participants will be collected, and their demographic characteristics, disease and medication history, gastrointestinal status, dietary habits, lifestyle habits, and mental health information will be recorded. Another 200 specimens will be collected from patients with parenteral virus infection. The demographic characteristics and pathogen test results of the parenteral virus infected patients will be reviewed and recorded. By virus metagenomic sequencing on fecal specimens, investigators will identify which viruses can be detected in the intestinal tract of apparently healthy people, and to explore whether parenteral infection viruses can be detected in feces.

Inclusion Criteria:

1. age ranged from 18 to 75 years;
2. no obvious symptoms and signs of the disease;
3. not taking a drug for a long time;
4. good psychological condition ;
5. no unhealthy lifestyle;
6. willing to participate in the study, sign the informed consent, fill out the questionnaire and provide fecal samples.

Exclusion Criteria:

1. pregnant and lactating women;
2. suffering from certain diseases, such as cardiovascular disease, digestive system disease and nervous system disease.

Apparent healthy people are those who do not have clinically obvious symptoms and signs, but may have underlying health problems or premorbid conditions.