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ARCHIVE H7N9 situation update

25 April 2018, 17:00 hours; Rome

The next update will be issued on 23 May 2018

Disclaimer

Information provided herein is current as of the date of issue. Information added or changed since the last H7N9 situation update appears in red. Human cases are depicted in the geographic location of their report. For some cases, exposure may have occurred in one geographic location but reported in another. For cases with unknown onset date, reporting date was used instead. FAO compiles information drawn from multiple national (Ministries of Agriculture or Livestock, Ministries of Health, Provincial Government websites; Centers for Disease Prevention and Control [CDC]) and international sources (World Health Organization [WHO], World Organisation for Animal Health [OIE]) as well as peer-reviewed scientific articles. FAO makes every effort to ensure, but does not guarantee, accuracy, completeness or authenticity of the information. The designation employed and the presentation of material on the map do not imply the expression of any opinion whatsoever on the part of FAO concerning the legal or constitutional status of any country, territory or sea area, or concerning the delimitation of frontiers.

 

 Overview

Hazard: Influenza A(H7N9) virus with pandemic potential.
Country: China; imported cases in Malaysia (1) and Canada (2).
Number of human cases: 1,625 confirmed; 623 deaths (since February 2013).
New findings in birds / environment since last update (28 March 2018): 2

New human cases since last update (28 March 2018): 0

Map 1. Human cases and positive findings in birds or the environment

Human cases and positive findings in birds or the environment
Click to enlarge - Note: Human cases are depicted in the geographic location where they were reported; for some cases, exposure may have occurred in a different geographic location. Precise location of 63 human cases in Anhui (2), Beijing (2), Guangdong (1), Guangxi (1), Hebei (3), Hunan (1), Hubei (2), Jiangsu (2), Jiangxi (6), Sichuan (2), Zhejiang (3) and unknown (38) Provinces are currently not known, these cases are therefore not shown on the map.

 

Provinces/municipalities affected: Beijing, Chongqing, Shanghai and Tianjin Municipalities; Anhui, Fujian, Gansu, Guangdong, Guizhou, Hebei, Heilongjiang, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Jilin, Liaoning, Qinghai, Shaanxi, Shanxi, Shandong, Sichuan, Taiwan, Yunnan and Zhejiang Provinces; Hong Kong SAR, Macao SAR; Guangxi, Inner Mongolia, Ningxia Hui, Tibet and Xinjiang Uyghur Autonomous Regions (China); Sabah (Malaysia); British Columbia (Canada).

Highly pathogenic virus findings: Since 10 January 2017, highly pathogenic avian influenza (HPAI) type H7N9 virus was detected in a total of 56 poultry or environmental samples (44 chickens, 2 duck and 10 environmental samples); H7N9 virus isolates from 32 human cases were found to be HPAI virus.

 

Table. Number of locations testing positive for H7N9 HPAI virus (n=41) in birds and/or the environment, by province and sampling site as of 25 April 2018.

Province

LBM*

Farm

Backyard

Airport

Total

Anhui

0

1

0

0

1

Fujian

1

0

0

0

1

Guangdong

22

0

0

0

22

Guangxi

0

1

0

0

1

Hebei

0

1

0

0

1

Heilongjiang

0

1

0

0

1

Henan

0

1

0

0

1

Hunan

3

1

1

0

5

Inner Mongolia

0

2

0

0

2

Ningxia Hui

0

1

0

0

1

Shaanxi

0

2

0

0

2

Shanxi

0

1

0

0

1

Tianjin

0

1

0

0

1

Unknown

0

0

0

1

1

TOTAL

26

13

1

1

41

*LBM: live bird market

 

 Situation update

Animals

  • 17 April 2018, Ningxia Hui Autonomous Region: An H7N9 HPAI outbreak occurred on 3 April in a layer chicken farm in Tongxin County, Wuzhong City. Of the 1200 birds that showed clinical signs, 585 died. [reference 1, reference 2].
  • 27 March 2018, Shanxi Province: An H7N9 HPAI outbreak occurred on 23 March in a layer chicken farm in Hongdong County, Linfen City, where 812 birds were found sick of which 699 died [reference 1, reference 2].

Animal/environmental findings: Since 4 April 2013 around 2500 virological samples from the environment, chickens, pigeons, ducks, a tree sparrow and a magpie robin tested positive; positives mainly from live bird markets, vendors and some commercial or breeding farms.

Figure 1. Number of positive virological samples from birds or the environment, by province and origin as of 25 April 2018. Data include both high and low pathogenic H7N9 viruses.

Number of positive virological samples from birds or the environment, by province* and origin
Click to enlarge

Figure 2. Distributions of low* and highly pathogenic H7N9 virologically positive samples (nLPAI=245; nHPAI=41) collected from birds or the environment, by sampling location, between October 2016 and 25 April 2018. Samples from the same location and time are grouped.

Number of positive virological samples from birds or the environment, by province* and origin
Click to enlarge - *may contain unconfirmed HPAI at the time of publishing

Figure 3. Distributions of low* and highly pathogenic H7N9 virologically positive samples (nLPAI=279; nHPAI=47) collected from birds or the environment, by sample origin between October 2016 and 25 April 2018. Samples from the same origin, location and time are grouped. Incidence of officially reported human cases by week, based on onset date

Click to enlarge - *may contain unconfirmed HPAI at the time of publishing

 

Humans

  • Since the last update (28 March 2018), no new human case was reported.
  • For detailed informationon human cases, please refer to WHO report.

Figure 4. Number of officially reported human cases since February 2013 as of 25 April 2018. Data include both high and low pathogenic H7N9 viruses

Incidence of officially reported human cases by week, based on onset date
Click to enlarge

Figure 5. Incidence of officially reported human cases by month, based on onset date from October 2013 (Beginning of wave 2) to 25 April 2018. Both high and low pathogenic H7N9 viruses are included.

Incidence of officially reported human cases by week, based on onset date
Click to enlarge - Note: For cases with unknown onset dates from wave 2 (n=2), wave 3 (n=146), wave 4 (n=27) and wave 5 (n=55), reporting dates were used instead.


For a phylogenetic tree of H7N9 viruses isolated please click here. Acknowledgements:WHO report ‘Antigenic and genetic characteristics of zoonotic influenza viruses and development of candidate vaccine viruses for pandemic preparedness’ – September 2017 [reference].

 

Publications  

  • Yang Q., Shi W., Zhang L., Xu Y., Xu J., Li S., […], Tian H. Westward Spread of Highly Pathogenic Avian Influenza A(H7N9) Virus among Humans, China. Emerging Infectious Diseases. 2018 June 17;24(6). doi: 10.3201/eid2406.171135. [reference]. The study reports infection of humans with highly pathogenic avian influenza A(H7N9) virus in Shaanxi, China, in May 2017. Complete genomes were obtained for samples from 5 patients and from live poultry markets or farms in four cities. Phylogenetic analyses support that the H7N9 LPAI viruses in Shaanxi Province originated from eastern and southern China, and the Shaanxi H7N9 HPAI isolates probably originated in Guangdong Province and were transmitted either directly or indirectly through other provinces.
  • Sun B., Wu M., Zhu C., Chen D., Zheng W., Wu K. Surveillance and Analysis of Bird Flu in Live Poultry Sites in Wenzhou, Zhejiang Province, 2011-2016. Disease Surveillance, 2017, 32(4): 328-331. Disease Surveillance, 2017, 32 (4): 328-331. [reference]. The study aimed at understanding the classification, composition and distribution characteristics of avian influenza viruses in surveillance sites in Wenzhou, Zhejiang Province. A total of 1885 specimens were collected from the surveillance sites of poultry in Wenzhou area. Amongst the different results, the positive rates of H5, H7, and H9 subtypes were 9.8%, 15.3%, and 8.6%, respectively. The average positive rate of H7N9 in poultry sites was 11.6%.
  • Yao J., Gu M.H., Qian C., Jiangyin Center for Disease Prevention and Control. Analysis of avian influenza in live poultry trading market in Jiangyin from 2014 to 2016. Modern Preventive Medecine, Editorial Email, 2018 June. [reference]. The study aimed at understanding the infection status of avian influenza A virus in occupational exposure populations and external environments in Jiangyin. Environmental samples were collected from the external environment, with a total AIV positive rate of 48.87%. Occupationally exposed populations were asked to respond to a questionnaire and sampled to detect HI antibodies of avian influenza subtypes. The awareness about protection measures was found to be poor. The total positive rate of HI antibodies against avian influenza virus subtypes was 18.75%.
  • Zhu W., Dong J., Zhang Y., Yang L., Li X., Chen T., […], Wang D. A Gene Constellation in Avian Influenza A (H7N9) Viruses May Have Facilitated the Fifth Wave Outbreak in China. Cell Reports. 2018 April 17; 23(3):909-917. doi: 10.1016/j.celrep.2018.03.081. [reference]. Based on an evolutionary analysis of H7N9 viruses from all five waves, the study showed that additional subclades of the H7 and N9 genes have emerged. Analysis indicates that H7N9 viruses inherited NP genes from co-circulating H7N9 instead of H9N2 viruses. Genotypic diversity among H7N9 viruses increased following wave 1, peaked during wave 3, and rapidly deceased thereafter with minimal diversity in wave 5, suggesting that the viruses entered a relatively stable evolutionary stage. The largest outbreak of wave 5 that was caused by the ZJ11 genotype may have been the consequence of a new constellation of genes rather than a single mutation.
  • Quan C., Shi W., Yang Y., Yang Y., Liu X., Xu W., […], Bi Y. New threats of H7N9 influenza virus: the spread and evolution of highly and low pathogenic variants with high genomic diversity in Wave Five. Journal of Virology. 2018 March 21. pii: JVI.00301-18. doi: 10.1128/JVI.00301-18. [reference]. In this study, the geographical distribution, phylogeny and genetic evolution of 240 H7N9 viruses in wave 5, including 35 new isolates, from patients and poultry in nine provinces, were comprehensively analyzed together with strains from the first four waves. The enhanced prevalence and diverse genetic characteristics with mammalian-adapted and NAI-resistant mutations may have contributed towards the increased number of human infections in wave 5.

FAO actions:

  • FAO published a risk assessment update entitled, “Chinese-origin H7N9 avian influenza: spread in poultry and human exposure” [reference]
  • FAO guidance and risk assessments are available on a dedicated website [link]
  • Liaise with China and partners, monitor situation, monitor virus evolution, conduct market chain analysis, risk assessment, surveillance guidance and communication.

FAO’s support to countries