Weekly Report
week 21 2016
Article source： Date time：2016-07-01
Chinese Influenza Weekly Report
(All data are preliminary and may change as more reports are received)
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Summary l During week 21, influenza activity in south China was low with influenza B detections predominating. In north China, there was almost no influenza activity detected. l Among influenza viruses antigenically characterized by CNIC since October, 2015, 602(96.9%) influenza A(H1N1)pdm09 viruses were characterized as A/California/7/2009-like; 139(51.9%) influenza A(H3N2) viruses were characterized as A/Switzerland/9715293/2013 (H3N2)(EGG)-like,232(86.6%) influenza A(H3N2) viruses were characterized as A/Switzerland/9715293/2013 (H3N2)(CELL)-like; 448(99.1%) influenza B/Yamagata viruses were characterized as B/Phuket/3073/2013-like. 373(62.9%) 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 October, 2015, 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 2 influenza A(H1N1)pdm09 viruses were sensitive to neuraminidase inhibitors. |
Outbreak Surveillance
During week 21(May 23–29, 2016), there was 8outbreaks reported nationwide, 5 of them were B, 1 of them was mixed,1 of them was other respiratory viruses, 1 of them was negative.
Surveillance of outpatient or emergency visits for Influenza-like Illness (ILI)
During week 21, the percentage of outpatient or emergency visits for ILI (ILI %) at national sentinel hospitals in south China was 3.3% , lower than last week 3.4% ,same as the same week of 2014 and 2015（3.3% and 3.3%）. (Figure 1)
Figure 1. Percentage of Visits for ILI at Sentinel Hospitalsin South China
(2012-2016)
During week 21, ILI% at national sentinel hospitals in north China was 2.4%,same as last week 2.4%,lower than the same week of 2014（2.5%）,and higher than the same week of 2015（2.3%）,. (Figure 2)
Figure 2. Percentage of Visits for ILI at Sentinel Hospitals in North China
(2012-2016)
Virologic Surveillance
During week 21,influenza network laboratories tested 3431 specimens, of which 187(5.5%) were positive for influenza, influenza A and influenza B viruswere19(10.2%) and168(89.8%), respectively (Table 1). During week 21, the percentage of specimens that were tested positive for influenza in south China was 6.5%, which was lower than the previous week (8.4%) (Figure 3).During week 21, the percentage of specimens that were tested positive for influenza in north China was 1.4%, which was lower than the previous week (1.9%)(Figure 4).
Table 1Laboratory Detections of ILI Specimens (Week 21, 2016)
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Week 21 |
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South China |
North China |
Total |
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No. of specimens tested |
2727 |
704 |
3431 |
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No. of positive specimens (%) |
177(6.5%) |
10(1.4%) |
187(5.5%) |
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Influenza A |
19(10.7%) |
0(0) |
19(10.2%) |
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A(H3N2) |
1(5.3%) |
0(0) |
1(5.3%) |
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A(H1N1)pdm09 |
18(94.7%) |
0(0) |
18(94.7%) |
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A (subtype not determined) |
0(0) |
0(0) |
0(0) |
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Influenza B |
158(89.3%) |
10(100%) |
168(89.8%) |
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B (lineage not determined) |
39(24.7%) |
0(0) |
39(23.2%) |
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Victoria |
103(65.2%) |
10(100%) |
113(67.3%) |
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Yamagata |
16(10.1%) |
0(0) |
16(9.5%) |
Figure 3. Influenza Positive Tests Reported by Southern Network Laboratories (Week 14, 2015–Week 21, 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 21, 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 October 1st, 2015, 602(96.9%) of the 621 A(H1N1)pdm09 viruses tested were characterized as A/California/7/2009-like;139(51.9%) of the 268A(H3N2) influenza viruses tested were characterized as A/Switzerland/9715293/2013 (H3N2)(EGG)-like, 232(86.6%) of the 268A(H3N2) influenza viruses tested were characterized as A/Switzerland/9715293/2013 (H3N2)(CELL)-like; 448(99.1%) of the 452 influenza B/Yamagata lineage viruses tested were characterized as B/Phuket/3073/2013-like; 373(62.9%) of the593 influenza B/Victoria lineage viruses tested have been characterized as B/Brisbane/60/2008-like.
Antiviral Resistance
Since October 1st, 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 influenza A(H3N2) and B viruses were sensitive to neuraminidase inhibitors. All but 2 influenza A(H1N1)pdm09 viruses were sensitive to neuraminidase inhibitors.
