Weekly Report

Week 16 2019

Article source: Date time:2019-04-27 
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Chinese Influenza Weekly Report

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

Summary

During week 16, influenza activity level continued to decrease in south China, but remained at a high level in most north provinces. At present, B-Victoria lineage was currently the dominant detected virus, followed by few A(H3N2) virus detections.

Among influenza viruses antigenically characterized by CNIC since October 1st, 2018, 1387(96.9%) influenza A(H1N1)pdm09 viruses were characterized as A/Michigan/45/2015-like; 241(75.5%) influenza A(H3N2) viruses were characterized as A/Singapore/INFIMH-16-0019/2016 (EGG)-like, 297(93.1%) influenza A(H3N2) viruses were characterized as A/Singapore/INFIMH-16-0019/2016 (CELL)-like; 60(31.6%) influenza B/Victoria viruses were characterized as B/Colorado/06/2017-like; 45(100.0%) influenza B/Yamagata viruses were characterized as B/Phuket/3073/2013-like.

Among the influenza viruses tested by CNIC for antiviral resistance analysis since October 1st, 2018, all influenza A(H1N1)pdm09 and A(H3N2) viruses were resistant to adamantine; All influenza A(H3N2) and B viruses were sensitive to neuraminidase inhibitors. All but 9 influenza A(H1N1)pdm09 were sensitive to neuraminidase inhibitors.

 

 

 

 

 

 

 

 

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

During week 16, the percentage of outpatient or emergency visits for ILI (ILI %) at national sentinel hospitals in southern provinces was 4.2%, higher than the last week (4.0%), higher than the same week of 2016-2018 (3.6%, 3.2% and 3.6%). (Figure 1)

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

(2016-2020)

During week 16, ILI% at national sentinel hospitals in northern provinces was 3.6%, lower than the last week (3.7%), higher than the same week of 2016-2018 (2.4%, 2.5% and 2.4%). (Figure 2)

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

(2016-2020)

Virologic Surveillance

During week 16, influenza network laboratories tested 4781 specimens, of which 1352(28.3%) were positive for influenza, influenza A and influenza B viruses were 275(20.3%) and 1077(79.7%), respectively (Table 1). During week 16, the percentage of specimens that were tested positive for influenza in south China was 23.5%, which was lower than the previous week (25.5%)(Figure 3). During week 16, the percentage of specimens that were tested positive for influenza in north China was 41.1%, which was higher than the previous week (39.0%). (Figure 4).

Table 1 Laboratory Detections of ILI Specimens (Week 16, 2019)

 

Week 16

South China

North China

Total

No. of specimens tested

3471

1310

4781

No. of positive specimens (%)

814(23.5%)

538(41.1%)

1352(28.3%)

Influenza A

162(19.9%)

113(21.0%)

275(20.3%)

A(H3N2)

110(67.9%)

99(87.6%)

209(76.0%)

A(H1N1)pdm09

51(31.5%)

13(11.5%)

64(23.3%)

A (subtype not determined)

1(0.6%)

1(0.9%)

2(0.7%)

Influenza B

652(80.1%)

425(79.0%)

1077(79.7%)

B (lineage not determined)

16(2.5%)

13(3.1%)

29(2.7%)

Victoria

630(96.6%)

412(96.9%)

1042(96.8%)

Yamagata

6(0.9%)

0(0)

6(0.6%)

Figure 3. Influenza Positive Tests Reported by Southern Network Laboratories (Week 14, 2018–Week 16, 2019)

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, 2018–Week 16, 2019)

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, 2018, 1387(96.9%) influenza A(H1N1)pdm09 viruses were characterized as A/Michigan/45/2015-like; 241(75.5%) influenza A(H3N2) viruses were characterized as A/Singapore/INFIMH-16-0019/2016 (EGG)-like, 297(93.1%) influenza A(H3N2) viruses were characterized as A/Singapore/INFIMH-16-0019/2016 (CELL)-like; 60(31.6%) influenza B/Victoria viruses were characterized as B/Colorado/06/2017-like; 45(100.0%) influenza B/Yamagata viruses were characterized as B/Phuket/3073/2013-like.

Antiviral Resistance

Since October 1st, 2018, among the influenza viruses tested by CNIC for antiviral resistance, all influenza A(H1N1)pdm09 and A(H3N2) viruses were resistant to adamantine; All influenza A(H3N2) and B viruses were sensitive to neuraminidase inhibitors. All but 9 influenza A(H1N1)pdm09 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 1567 laboratory-confirmed cases have been reported to WHO. Among them, 33 cases were infected with HPAI A(H7N9) virus, which have mutations in the hemagglutinin gene indicating a change to high pathogenicity in poultry. These 33 cases are from Taiwan (the case had travel history to Guangdong), Guangxi, Guangdong, Hunan, Shaanxi, Hebei, Henan, Fujian, Yunnan, Inner Mongolia.

No increased transmissibility or virulence to human case was detected in the HPAI A(H7N9) virus.