Weekly Report

Week 11 2017

Article source: Date time:2017-03-27 
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Chinese Influenza Weekly Report

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

Summary

During week 11, influenza activity was still a little high in southern and northern China with A(H3N2) and A(H1N1)pdm09 virus epidemic, and A(H1N1)pdm09 viruses had exceeded A(H3N2) .

Among influenza viruses antigenically characterized by CNIC since September, 2016, 244(100%) influenza A(H1N1)pdm09 viruses were characterized as A/California/7/2009-like; 230(99.6%) influenza A(H1N1)pdm09 viruses were characterized as A/Michigan/45/2015-like; 227(48.5%) influenza A(H3N2) viruses were characterized as A/Hong Kong/4801/2014 (H3N2)(EGG)-like,457(97.6%) 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.

 

 

Outbreak Surveillance

During week 11(Mar 13th- Mar 19th, 2017), there were 30 outbreaks reported nationwide, 7 of them were A(H1N1),2 of them were A(H3N2),16 of them were B ,1 of them was mixed, 2 of them were negative, 2 of them were untyped.

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

During week 11, the percentage of outpatient or emergency visits for ILI (ILI %) at national sentinel hospitals in south China was 3.0%, same as last week 3.0% higher than the same week of 2015 (2.5%), lower than the same week of 2016 3.9%. (Figure 1)

Figure 1. Percentage of Visits for ILI at Sentinel Hospitals in South China

(2012-2017)

During week 11, ILI% at national sentinel hospitals in north China was 3.4%, higher than last week and the same week of 2015 (3.2% both 2.5%), lower than the same week of 20164.0%. (Figure 2)

Figure 2. Percentage of Visits for ILI at Sentinel Hospitals in North China

(2012-2017)

Virologic Surveillance

During week 11, influenza network laboratories tested 6671 specimens, of which 1112(16.7%) were positive for influenza, influenza A and influenza B viruses were 891(80.1%) and 221(19.9%), respectively (Table 1). During week 11, the percentage of specimens that were tested positive for influenza in south China was 14.0%, which was higher than the previous week (13.1%) (Figure 3). During week 11, the percentage of specimens that were tested positive for influenza in north China was 19.6%, which was higher than the previous week (18.2%). (Figure 4).

Table 1 Laboratory Detections of ILI Specimens (Week 11, 2017)

 

Week 11

South China

North China

Total

No. of specimens tested

3439

3232

6671

No. of positive specimens (%)

480(14.0%)

632(19.6%)

1112(16.7%)

Influenza A

281(58.5%)

610(96.5%)

891(80.1%)

A(H3N2)

107(38.1%)

154(25.2%)

261(29.3%)

A(H1N1)pdm09

170(60.5%)

455(74.6%)

625(70.1%)

A (subtype not determined)

4(1.4%)

1(0.2%)

5(0.5%)

Influenza B

199(41.5%)

22(3.5%)

221(19.9%)

B (lineage not determined)

11(5.5%)

2(9.1%)

13(5.9%)

Victoria

161(80.9%)

10(45.5%)

171(77.4%)

Yamagata

27(13.6%)

10(45.5%)

37(16.7%)

 

Figure 3. Influenza Positive Tests Reported by Southern Network Laboratories (Week 14, 2015–Week 11, 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.

Figure 4. Influenza Positive Tests Reported by Northern Network Laboratories (Week 14, 2015–Week 11, 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 1st, 2016, all of the 244 A(H1N1)pdm09 viruses tested were characterized as A/California/7/2009-like; 230(99.6%) of the 231 A(H1N1)pdm09 viruses tested were characterized as A/Michigan/45/2015-like;227(48.5%) of the 468 A(H3N2) influenza viruses tested were characterized as A/Hong Kong/4801/2014 (H3N2)(EGG)-like, 457(97.6%) of the 468 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 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(H1N1)pdm09 and all influenza A(H3N2) and B viruses were sensitive to neuraminidase inhibitors.