In urban comprehensive hospitals, internal medicine department, internal emergency room, fever clinic and/or internal pediatric clinic, internal pediatric emergency room have duties of monitoring influenza liked cases.

In urban pediatric hospitals, the internal pediatric clinic, internal pediatric emergency room and fever clinics have the duties of monitoring influenza liked cases.

Internal medicine clinics monitoring influenza liked cases should include all internal clinic consultation rooms.

If the internal pediatric clinic in the sentinel hospitals has subdivided sections, all the internal pediatric clinic consultation rooms have duties in monitoring influenza liked cases.

According to the definition of influenza liked cases, medical staffs in monitoring consultation rooms of sentinel hospitals must record the number of influenza liked cases found in each age group and in each department. And the total number of cases found in clinics and emergency rooms should also be recorded. The department in charge in sentinel hospital should collect the data everyday and input the data into Chinese Surveillance System of Influenza on Mondays.

The number of influenza liked cases and hospital total number of clinic/emergency room visits should have consistent source from each monitoring consultation rooms.

The sentinel hospitals have rights to determine the department in charge.

Subjects of sampling: influenza liked cases who show symptoms within 3 days with no use of any anti-viral drugs.

The sentinel hospital should collect 20–30 specimens per week. The collection time should be evenly distributed to avoid focused and sudden sampling. Sampling can be performed every other day, with 7–10 samples collected on the day. Sampling may also be performed each day, with 4–6 samples collected on the day. The specimens should be kept at the temperature of below 4 °C. For each week, samples should be sent to the network laboratories at least twice.

After influenza surveillance network laboratories receive the samples by routine collection from sentinel hospitals, it is required to process the samples and test the nucleic acid within 48 h. The samples with positive findings should be performed isolation and identification of Influenza A (H1N1) virus in laboratories with biological safety and testing conditions. All the influenza strains should be sent to provincial CDC for reservation and identification. The provincial CDC is required to send all Influenza A (H1N1) strains with HA titer no less than 8 (including seasonal flu viruses) to national influenza center and the virus culture fluid should be no less than 3 mL/strain. Within 4 weeks of samples collection, the virus strain should be sent out.

The provincial CDC and other influenza surveillance network laboratories with required biological safety and testing conditions should isolate Influenza A (H1N1) virus from samples.

The influenza surveillance network laboratories should send positive samples with unidentifiable virus types and subtypes to national influenza center within 48 h.

After laboratory testing, the samples information, nucleic acid testing, virus isolation and identification must be input into the Chinese Influenza Surveillance Information System within 24 h.

After influenza surveillance network laboratories receive samples from epidemic outbreaks, the samples should be processed for nucleic acid tests within 24 h. The Influenza A (H1N1) viruses should be isolated and identified in laboratories with biological safety and testing conditions. All the Influenza A (H1N1) virus strains with HA titer no less than 8 should be sent to national influenza center, with the virus culture fluid no less than 3 mL/strain. Within 4 weeks of samples collection, the virus strain should be sent out. At least five positive specimens should be performed virus isolation for each epidemic outbreak. If the collected specimens are less than five, all specimens should be performed virus isolation.

Within 1 week, occurrence of five or more cases of clustering acute fever and respiratory infection that is associated with epidemiology in the places where the same group of people clustering (such as schools, kindergartens, hospitals, homes for the aged, factory and construction sites) should be reported within 2 h to county CDC. The outbreak in rural areas can also be reported to the local village or town hospitals.

Once county (district) CDC receives the epidemic report, it has the responsibilities to organize preliminary investigation and verification immediately, followed by collection of the patients’ samples, tests of the samples in appropriate laboratories to detect seasonal flu viruses and Influenza A (H1N1) viruses. The amount of samples collected should be enough for laboratory diagnosis of the epidemic. Generally, for clustering epidemic of less than 20 cases, samples from all cases should be collected; for clustering epidemic of more than 20 cases, only samples from no more than 20 cases should be collected. Patients with acute fever and respiratory infection but no definitive laboratory diagnosis in the same epidemic event can be diagnosed as clinical cases when other diseases causing flu liked symptoms are excluded.

The definitively diagnosed cases of seasonal flu or Influenza A (H1N1) meet the following at least one criterion should be reported in the forms of Information Report of Sudden Public Health Events and Epidemic Outbreak Report of Seasonal Flu and Influenza A (H1N1) by county (district) CDC in 2 h. Direct internet reporting may also be performed in Sudden Public Health Events Reporting System. The province (district or city) can adjust reporting standards according to local epidemic situation. The direct internet reporting of Reporting Form for Epidemic Outbreak Surveillance for Flu Liked Cases has been terminated.

The definitively diagnosed cases in the outbreak event should be relevant to individual case in Disease Surveillance Information Reporting Management System. The definitively diagnosed cases that have not reported in the system should be supplementary reported.

The network laboratories responsible to laboratory tests should input the laboratory testing results into Chinese Influenza Surveillance Information System. The CDC reporting the epidemic should relate the samples information to the individual case of Disease Surveillance Information Reporting Management System.

During the process of investigation and management of epidemic outbreak, various levels of CDC should timely revise the initial report in Outbreak Reporting Form of Seasonal Flu and Influenza A (H1N1). The progress reports and final reports should be well finished according to the requirements in Management Standards of National Sudden Public Health Events Information Reporting.