Weekly Report

Week 31 2020

Article source: Date time:2020-08-07 
Download:China flu report 2031.pdf

Chinese Influenza Weekly Report

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

Summary

During week 31, the influenza activity in mainland China was still at a very low level, there was almost no positive specimen detected.

Among influenza viruses antigenically characterized by CNIC since October 1st, 2019, 809(96.2%) influenza A(H1N1)pdm09 viruses were characterized as A/Brisbane/02/2018-like; 47(3.8%) influenza A(H3N2) viruses were characterized as A/Kansas/14/2017 (EGG)-like, 101(8.3%) influenza A(H3N2) viruses were characterized as A/Kansas/14/2017 (CELL)-like; 183(16.9%) influenza B/Victoria viruses were characterized as B/Colorado/06/2017-like; 2(100%) 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, 2019, 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 1 influenza A(H1N1)pdm09 were sensitive to neuraminidase inhibitors.

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

During week 31(Jul 27th 2020 –Aug 2nd 2020), the percentage of outpatient or emergency visits for ILI (ILI%) at national sentinel hospitals in southern provinces was 2.7%, same as the last week (2.7%), lower than the same week of 2017-2019 (3.5%, 3.0% and 3.3%). (Figure 1)

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

(2017-2021)

During week 31, ILI% at national sentinel hospitals in northern provinces was 2.0%, same as the last week (2.0%), lower than the same week of 2017-2019 (2.5%, 2.1% and 2.2%). (Figure 2)

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

(2017-2021)

 

Virologic Surveillance

During week 31, influenza network laboratories tested 4586 specimens, there were two positive for influenza. The number and proportion of influenza types and subtypes detected in southern and northern provinces are shown in Table 1.

Table 1  Laboratory Detections of ILI Specimens (Week 31, 2020)

 

Week 31

South China

North China

Total

No. of specimens tested

3556

1030

4586

No. of positive specimens (%)

2(0.1%)

0(0)

2(0)

Influenza A

1

0

1

A(H3N2)

0

0

0

A(H1N1)pdm09

1

0

1

A (subtype not determined)

0

0

0

Influenza B

1

0

1

B (lineage not determined)

0

0

0

Victoria

1

0

1

Yamagata

0

0

0

Figure 3. Influenza Positive Tests Reported by Southern Network Laboratories (Week 14, 2019–Week 13, 2021)

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, 2019–Week 13, 2021)

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, 2019, 809(96.2%) influenza A(H1N1)pdm09 viruses were characterized as A/Brisbane/02/2018-like; 47(3.8%) influenza A(H3N2) viruses were characterized as A/Kansas/14/2017 (EGG)-like, 101(8.3%) influenza A(H3N2) viruses were characterized as A/Kansas/14/2017 (CELL)-like; 183(16.9%) influenza B/Victoria viruses were characterized as B/Colorado/06/2017-like; 2(100%) influenza B/Yamagata viruses were characterized as B/Phuket/3073/2013-like.

Antiviral Resistance

Since October 1st, 2019, 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 1 influenza A(H1N1)pdm09 were sensitive to neuraminidase inhibitors.

Outbreak Surveillance

During week 31 (Jul 27th - Aug 2nd 2020), there was no ILI outbreak reported nationwide.

H7N9 Case Report

During week 31, no new human infection with novel reassortant influenza A(H7N9) virus was reported.