Font: Small Medium Large [print] Release: 2015-12-29 13:23:07 Submitter: YangLei hits：33

Chinese Influenza Weekly Report

(All data are preliminary and may change as more reports are received)

Outbreak Surveillance

During week 50 (December 7–13, 2015), there were 8 outbreaks reported nationwide, 2 of them were A(H1N1)pdm, 1 of them was A(H3N2), 1 of them was B ,and 4 were negative.

Surveillance of outpatient or emergency visits for Influenza-like Illness (ILI)

During week 50, the percentage of outpatient or emergency visits for ILI (ILI %) at national sentinel hospitals in south China was 2.6%, same as last week（2.6%），higher than 2011、2012 and 2014（2.4%、2.2% and 2.3%）, lower than 2013（2.7%）.(Figure 1)

Figure 1. Percentage of Visits for ILI at Sentinel Hospitals in South China (2011-2016)

During week 50, ILI% at national sentinel hospitals in north China was 2.6%, higher than the last week (2.5%), lower than 2011-2014 （2.6%、3.3%、3.0%and 3.7%）. (Figure 2)

Figure 2. Percentage of Visits for ILI at Sentinel Hospitals in North China (2011-2016)

Virologic Surveillance

During week 50, influenza network laboratories tested 6629 specimens, of which 286(4.3%) were positive for influenza, influenza A and influenza B virus were 210(73.4%) and 76(26.6%)，respectively(Table 1). During week 50, the percentage of specimens that were tested positive for influenza in south China was 4.2%, which was slightly lower than the previous week (4.5%)(Figure 3).During week 50, the percentage of specimens that were tested positive for influenza in north China was 4.5%, which was higher than the previous week (3.3%)(Figure 4).

Figure 3. Influenza Positive Tests Reported by Southern Network Laboratories (Week 14, 2014–Week 50, 2015)

Note: Analysis in this part was based on the test results of network laboratories. If it were not consistent with the results of CNIC confirmation, the results of CNIC confirmation were used.

Figure 4. Influenza Positive Tests Reported by Northern Network Laboratories (Week 14, 2014–Week 50, 2015)

Note: Analysis in this part was based on the result of network laboratories. If it were not consistent with the results of CNIC confirmation, the results of CNIC confirmation were used.

Antigenic Characterization

Since March 2^nd, 2015, all of the 22 A(H1N1)pdm09 viruses tested were characterized as A/California/7/2009-like; 76(25.9%) of the 293 A(H3N2) influenza viruses tested were characterized asA/Switzerland/9715293/2013 (H3N2)(EGG)-like; 682(94.5%) of the 722 influenza B/Yamagata lineage viruses tested were characterized as B/Phuket/3073/2013-like; 37(66.1%) of the 54 influenza B/Victoria lineage viruses tested have been characterized as B/Brisbane/60/2008-like.

Antiviral Resistance

Since March 2^nd, 2015, among the influenza viruses tested by CNIC for antiviral resistance, all influenza A(H1N1)pdm09 and all influenza A(H3N2) viruses were resistant to adamantine ; all but 4 influenza A(H3N2) viruses were sensitive to neuraminidase inhibitors, all but 2 influenza B viruses were sensitive to neuraminidase inhibitors, all influenza A(H1N1)pdm09 viruses were sensitive to neuraminidase inhibitors.