Human Infection with Avian Influenza

A(H7N9) Virus: Situation and

Response, ChinaZijian FENG

Center for Public Health Emergency Center Chinese Center for Disease Control and

Prevention

Overview of human H7N9 cases reported in Mainland China

One confirmed case was reported in Taiwan（ onset date: Apr 12) and he returned to Taipei from Suzhou via Shanghai 3 days before date of onset

Province No. of cases Death %

Zhejiang 48 11 24

Shanghai 33 18 55

Jiangsu 28 9 32

Jiangxi 6 1 17

Fujian 5 1 20

Anhui 4 2 50

Henan 4 1 25

Hunan 2 1 50

Shandong 2 0 0

Beijing 2 0 0

Hebei 1 0 0

Guangdong 1 0 0

Total 136 44 33

Epidemic curve of human H7N9 cases in Mainland China

2/12 2/22 3/4 3/14 3/24 4/3 4/13 4/23 5/3 5/13 5/23 6/2 6/12 6/22 7/2 7/12 7/22 8/1 8/110

2

4

6

8

10

HospitalizedRecoveredDeath

Onset date

No.

of c

ases

Onset date

No

. o

f c

as

es

HebeiJiangxiFujianShandongHunanBeijingHenanAnhuiJiangsuZhejiangShanghai

3 stages of the epidemic：• Feb 19～Mar

27, Sporadic

cases in Shanghai, Zhejiang, Jiangsu and Anhui;

• Mar 28～ Apr 18,

Increasing stage, spread to 10 provinces;

• Apr 19～Aug10,

Declined stage, sporadic cases.

Human H7N9 cases and deaths by sex and age

(as of 10 Aug 2013， 134 cases and 44 deaths)

Sex: Male 70%, Female 30%Age: median 62 yrs， range: 2～ 91yrs

Deaths

0～ 10～ 20～ 30～ 40～ 50～ 60～ 70～ 80～ 90～0

5

10

15

20

25

30M F

Age group

Nu

mb

er o

f ca

ses

0～ 10～ 20～ 30～ 40～ 50～ 60～ 70～ 80～ 90～0

3

6

9

Nu

mb

er o

f ca

ses

Age group

Virological features of H7N9 Virus:

• HA gene: Similar to H7N3 isolated from

duck in Zhejiang

• NA gene: Similar to H7N9 isolated from

wild bird in South Korea

All six internal genes: Shared highest similarity with

A/brambling/Beijing/16/2012-like

viruses (H9N2)Gao R, et al. N Engl J Med, 2013, 368(20):1888-97.

Serology study of H7N9 virus• Sera collected from 1544 poultry workers from Shanghai, Zhejiang,

Jiangsu and Anhui during Jan-Nov 2012, all tested negative for H7N9 specific antibody by MN

• Sera from 90 persons (30 children,30 adults and 30 elderly) before and after influenza vaccination for 2012-13 season, no pre-existing immunity for H7N9, no cross-reactive antibody against H7N9 virus

Bai T, Zhou J, Shu Y. N Engl J Med,2013,368(24):2339-2340; Zhou J, Wang D, Gao R, et al. Nature,2013.

Serological study in seven provinces (as of Aug 14)

　 No. serum HI positive ( titer≥160）（ %） MN( titer ≥20)（ %）Close contacts（ HCW） 48 0（ 0） 0（ 0）

Other close contacts 483 6(1.24) 2（ 0.41）Poultry workers** 1225 0（ 0） 0（ 0）

Note： study provinces included Henan, Shanghai, Hunan, Fujian, Shandong, Anhui, Jiangxi**269 serum specimens from poultry workers in Shanghai were excluded.

Exposure history of H7N9 cases（ N=133）

Types of Exposure Number (%)

Exposed to poultry or live market, n/N (%) 92/133(69%)

Exposed to mammal (pig, dog, cat, rabbit） 8/133(6%)

Poultry workers, n(%) 8/133(6%)

Exposure history of one case who was retrospectively diagnosed and reported on July 2 in Jiangsu, is unknown (onset date: Apr 25)

Risk factors of H7N9 infection• Case-control study in Jiangsu

– 25 cases, 93 controls; age, sex, and location were matched

– Risk factors: contact with poultry, birds (pigeon, quail) within 2 weeks before illness onset; with underlying chronic diseases ( exclude hypertension); environment exposure (visiting live market)

• National case-control study

– 89 cases, 340 controls; age, sex, and location were matched

– Risk factors: visiting live poultry market, direct/indirect contact with poultry, backyard poultry death, Obesity, COPD, long-term taking immunosuppressive medicationAi J, Huang Y, Xu K, et al. Euro Surveill. 2013;18(26):pii=20510.

Case-Control Study of Risk factors associated with H7N9 virus infections

(89 cases, 340 controls)