Weekly Report

Week 31 2017

Article source: Date time:2017-08-14 
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Chinese Influenza Weekly Report

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

Summary

During week 31, influenza activity peaked in most provinces in southern China with A(H3N2) circulating in the region, but it appeared to decrease. Almost no influenza activity was detected in northern China.

Among influenza viruses antigenically characterized by CNIC since September, 2016, 1508(99.6%) influenza A(H1N1)pdm09 viruses were characterized as A/California/7/2009-like;1393(92.8%) influenza A(H1N1)pdm09 viruses were characterized as A/Michigan/45/2015-like; 365(41.0%) influenza A(H3N2) viruses were characterized as A/Hong Kong/4801/2014 (H3N2)(EGG)-like,868(97.5%) influenza A(H3N2) viruses were characterized as A/Hong Kong/4801/2014 (H3N2)(CELL)-like; 723(91.3%) influenza B/Victoria viruses were characterized as  B/Brisbane/60/2008-like; 238(91.9%) 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 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 31(Jul 30- Aug 6 2017), there were four outbreaks reported nationwide, all of them were A(H3N2).

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

During week 31, the percentage of outpatient or emergency visits for ILI (ILI %) at national sentinel hospitals in southern China was 3.6%, lower than the last week and the same week of 2015(4.0%, 3.8%), higher than the same time of 2014 and 2016(3.4%, 2.8%).(Figure 1)

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

(2014-2018)

During week 31, ILI% at national sentinel hospitals in northern China was 2.5%, higher than the last week and the same of 2015 and 2016 (2.4%, 2.4%, 2.3%), same as the same week of 2014(2.5%). (Figure 2)

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

(2014-2018)

Virologic Surveillance

During week 31, influenza network laboratories tested 3978 specimens, of which 719(18.1%) were positive for influenza, influenza A and influenza B viruses were 685(95.3%) and 34 (4.7%), respectively (Table 1). During week 31, the percentage of specimens that were tested positive for influenza in south China was 22.0%, which was lower than the previous week (24.1%) (Figure 3). During week 31, the percentage of specimens that were tested positive for influenza in north China was 2.9%, which was slightly higher than the previous week (1.6%). (Figure 4).

Table 1 Laboratory Detections of ILI Specimens (Week 31, 2017)

 

Week 31

South China

North China

Total

No. of specimens tested

3157

821

3978

No. of positive specimens (%)

695(22%)

24(2.9%)

719(18.1%)

Influenza A

662(95.3%)

23(95.8%)

685(95.3%)

A(H3N2)

630(95.2%)

21(91.3%)

651(95.0%)

A(H1N1)pdm09

21(3.2%)

2(8.7%)

23(3.4%)

A (subtype not determined)

11(1.7%)

0(0)

11(1.6%)

Influenza B

33(4.7%)

1(4.2%)

34(4.7%)

B (lineage not determined)

3(9.1%)

0(0)

3(8.8%)

Victoria

20(60.6%)

0(0)

20(58.8%)

Yamagata

10(30.3%)

1(100%)

11(32.4%)

 

Figure 3. Influenza Positive Tests Reported by Southern Network Laboratories (Week 14, 2016–Week 31, 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, 2016–Week 31, 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, 1508(99.6%) of the 1514A(H1N1)pdm09 viruses tested were characterized as A/California/7/2009-like; 193(92.8%) of the 1501 A(H1N1)pdm09 viruses tested were characterized as A/Michigan/45/2015-like;365(41.0%) of the 890A(H3N2) influenza viruses tested were characterized as A/Hong Kong/4801/2014 (H3N2)(EGG)-like, 868(97.5%) of the 890A(H3N2) influenza viruses tested were characterized as A/Hong Kong/4801/2014 (H3N2)(CELL)-like; 723(91.3%) of the 792 influenza B/Victoria lineage viruses tested were characterized as B/Brisbane/60/2008-like; 238(91.9%) of the 259 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(H3N2) and B viruses were sensitive to neuraminidase inhibitors. All but 4 influenza A(H1N1)pdm09 viruses were sensitive to neuraminidase inhibitors.

H7N9 case report

Since the notification of human infection with novel reassortant influenza A(H7N9) virus on 31 March 2013, in total 1555 laboratory-confirmed cases have been reported to WHO.

Among 751 cases reported in fifth wave (Since Oct 2016), 25 cases were infected with HPAI A(H7N9) virus, which have mutations in the hemagglutinin gene indicating a change to high pathogenicity in poultry. These 25 cases are from Taiwan (the case had travel history to Guangdong), Guangxi, Guangdong and Hunan provinces, with illness onset date before April 2017. No increased transmissibility or virulence to human case was detected in the HPAI A(H7N9) virus.