Chinese Influenza Weekly Report (All data are preliminary and may change as more reports are received) Summary During week 13, influenza activity was still a little high in mainland China, and it was increasing in southern China with A(H1N1)pdm09 and B virus epidemic, but declining in northern China with A(H1N1)pdm09 epidemic. Among influenza viruses antigenically characterized by CNIC since September, 2016, 284(100%) influenza A(H1N1)pdm09 viruses were characterized as A/California/7/2009-like; 270(99.6%) influenza A(H1N1)pdm09 viruses were characterized as A/Michigan/45/2015-like; 260(39.0%) influenza A(H3N2) viruses were characterized as A/Hong Kong/4801/2014 (H3N2)(EGG)-like,649(97.3%) influenza A(H3N2) viruses were characterized as A/Hong Kong/4801/2014 (H3N2)(CELL)-like; 184(99.5%) influenza B/Victoria viruses were characterized as B/Brisbane/60/2008-like; 60(92.3%) influenza B/Yamagata viruses were characterized as B/Phuket/3073/2013-like. Among the influenza viruses tested by CNIC for antiviral resistance analysis since September, 2016, all influenza A(H1N1)pdm09 and all influenza A(H3N2) viruses were resistant to adamantine; All influenza A(H1N1)pdm09 and all influenza H3N2 and B viruses were sensitive to neuraminidase inhibitors. 1
Outbreak Surveillance During week 13(Mar 27 th - Apr 2 th, 2017), there were 44 outbreaks reported nationwide, 17 of them were A(H1N1), 7 of them were A(H3N2),14 of them were B,1 of them was negative, 5 of them were untyped. Surveillance of outpatient or emergency visits for Influenza-like Illness (ILI) During week 13, the percentage of outpatient or emergency visits for ILI (ILI %) at national sentinel hospitals in south China was 3.1%, higher than the last week and same week of 2015 (3.0% and 2.8%), lower than the same week of 2016(4.0%). (Figure 1) Figure 1. Percentage of Visits for ILI at Sentinel Hospitals in South China (2012-2017) During week 13, ILI% at national sentinel hospitals in north China was 3.3%, lower than the last week and same week of 2016 (3.4% and 3.7%), higher than the same week of 2015(2.6%). (Figure 2) 2
Figure 2. Percentage of Visits for ILI at Sentinel Hospitals in North China (2012-2017) Virologic Surveillance During week 13, influenza network laboratories tested 7113 specimens, of which 1033(14.5%) were positive for influenza, influenza A and influenza B viruses were 736(71.2%) and 297(28.8%), respectively (Table 1). During week 13, the percentage of specimens that were tested positive for influenza in south China was 15.2%, which was a little higher than the previous week (15.1%) (Figure 3). During week 11, the percentage of specimens that were tested positive for influenza in north China was 13.8%, which was lower than the previous week (15.1%). (Figure 4). Table 1 Laboratory Detections of ILI Specimens (Week 13, 2017) Week 13 South China North China Total No. of specimens tested 3654 3459 7113 No. of positive specimens (%) 555(15.2%) 478(13.8%) 1033(14.5%) Influenza A 276(49.7%) 460(96.2%) 736(71.2%) A(H3N2) 83(30.1%) 56(12.2%) 139(18.9%) A(H1N1)pdm09 191(69.2%) 404(87.8%) 595(80.8%) 3
A (subtype not determined) 2(0.7%) 0 2(0.3%) Influenza B 279(50.3%) 18(3.8%) 297(28.8%) B (lineage not determined) 16(5.7%) 0 16(5.4%) Victoria 234(83.9%) 6(33.3%) 240(80.8%) Yamagata 29(10.4%) 12(66.7%) 41(13.8%) Figure 3. Influenza Positive Tests Reported by Southern Network Laboratories (Week 14, 2015 Week 13, 2017) 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. 4
Figure 4. Influenza Positive Tests Reported by Northern Network Laboratories (Week 14, 2015 Week 13, 2017) 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 September 1 st, 2016, all of the 284 A(H1N1)pdm09 viruses tested were characterized as A/California/7/2009-like; 270(99.6%) of the 271 A(H1N1)pdm09 viruses tested were characterized as A/Michigan/45/2015-like;260(39.0%) of the 667A(H3N2) influenza viruses tested were characterized as A/Hong Kong/4801/2014 (H3N2)(EGG)-like, 649(97.3%) of the 667 A(H3N2) influenza viruses tested were characterized as A/Hong Kong/4801/2014 (H3N2)(CELL)-like; 184(99.5%) of the 185 influenza B/Victoria lineage viruses tested were characterized as B/Brisbane/60/2008-like; 60(92.3%) of the 65 influenza B/Yamagata lineage viruses tested were characterized as B/Phuket/3073/2013-like. Antiviral Resistance Since September 1 st, 2016, 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 influenza A(H1N1)pdm09 and all influenza A(H3N2) and B viruses were sensitive to neuraminidase inhibitors. 5