Weekly Report
Week 37 2016
Article source： Date time：2016-09-25
Download：Download:China flu report 1637.pdf
Chinese Influenza Weekly Report
(All data are preliminary and may change as more reports are received)
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Summary l During week 37, influenza activity level in mainland China was very low. Influenza viruses detected mainly were A(H3N2). There was few positive virus was detected in northern China. l Among influenza viruses antigenically characterized by CNIC since March, 2016, 277(98.9%) influenza A(H1N1)pdm09 viruses were characterized as A/California/7/2009-like;25(80.6%) influenza A(H3N2) viruses were characterized as A/Switzerland/9715293/2013 (H3N2)(EGG)-like,31(100%) influenza A(H3N2) viruses were characterized as A/Switzerland/9715293/2013 (H3N2)(CELL)-like; 196(98.5%) influenza B/Yamagata viruses were characterized as B/Phuket/3073/2013-like. 591(83.5%) influenza B/Victoria viruses were characterized as B/Brisbane/60/2008-like. l Among the influenza viruses tested by CNIC for antiviral resistance analysis since March, 2016, all influenza A(H1N1)pdm09 and all influenza A(H3N2) viruses were resistant to adamantine; all influenza H3N2 and B viruses were sensitive to neuraminidase inhibitors. All but 4 influenza A(H1N1)pdm09 viruses were sensitive to neuraminidase inhibitors. |
Outbreak Surveillance
During week 37 (Sep 12–18, 2016), there were 2 outbreaks reported nationwide, both of them were untyped.
Surveillance of outpatient or emergency visits for Influenza-like Illness (ILI)
During week 37, the percentage of outpatient or emergency visits for ILI (ILI %) at national sentinel hospitals in south China was 2.9% , higher than last week, the same week of 2014 and 2015（2.6%、2.7% and 2.5%）. (Figure 1)
Figure 1. Percentage of Visits for ILI at Sentinel Hospitals in South China
(2012-2016)
During week 37, ILI% at national sentinel hospitals in north China was 2.7%, higher than last week, the same week of 2014 and 2015（2.4%、2.5% and 2.1%）.. (Figure 2)
Figure 2. Percentage of Visits for ILI at Sentinel Hospitals in North China
(2012-2016)
Virologic Surveillance
During week 37, influenza network laboratories tested 2981 specimens, of which 165(5.5%) were positive for influenza, influenza A and influenza B virus were 155(93.9%) and 10(6.1%), respectively (Table 1). During week 37, the percentage of specimens that were tested positive for influenza in south China was 6.7%, which was higher than the previous week (5.4%) (Figure 3).During week 37, the percentage of specimens that were tested positive for influenza in north China was 0.5%, which was higher than the previous week (0.2%)(Figure 4).
Table 1 Laboratory Detections of ILI Specimens (Week 37, 2016)
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Week 37 |
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South China |
North China |
Total |
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No. of specimens tested |
2429 |
552 |
2981 |
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No. of positive specimens (%) |
162(6.7%) |
3(0.5%) |
165(5.5%) |
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Influenza A |
152(93.8%) |
3(100%) |
155(93.9%) |
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A(H3N2) |
148(97.4%) |
3(100%) |
151(97.4%) |
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A(H1N1)pdm09 |
4(2.6%) |
0(0) |
4(2.6%) |
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A (subtype not determined) |
0(0) |
0(0) |
0(0) |
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Influenza B |
10(6.2%) |
0(0) |
10(6.1%) |
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B (lineage not determined) |
3(30.0%) |
0(0) |
3(30.0%) |
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Victoria |
4(40.0%) |
0(0) |
4(40.0%) |
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Yamagata |
3(30.0%) |
0(0) |
3(30.0%) |
Figure 3. Influenza Positive Tests Reported by Southern Network Laboratories (Week 14, 2015–Week 37, 2016)
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, 2015–Week 37, 2016)
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 1st, 2016, 277(98.9%) of the 280 A(H1N1)pdm09 viruses tested were characterized as A/California/7/2009-like; 25(80.6%) of the 31 A(H3N2) influenza viruses tested were characterized as A/Switzerland/9715293/2013 (H3N2)(EGG)-like, all of the 31 A(H3N2) influenza viruses tested were characterized as A/Switzerland/9715293/2013 (H3N2)(CELL)-like; 196(98.5%) of the 199 influenza B/Yamagata lineage viruses tested were characterized as B/Phuket/3073/2013-like; 591(83.5%) of the 708 influenza B/Victoria lineage viruses tested have been characterized as B/Brisbane/60/2008-like.
Antiviral Resistance
Since March 1st, 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(H3N2) and B viruses were sensitive to neuraminidase inhibitors. All but 4 influenza A(H1N1)pdm09 viruses were sensitive to neuraminidase inhibitors.
