Circulation of Reassortant Influenza A(H7N9) Viruses in Poultry and Humans, Guangdong Province, China, 2013

Abstract

Influenza A(H7N9) virus emerged in eastern China in February 2013 and continues to circulate in this region, but its ecology is poorly understood. In April 2013, the Guangdong Provincial Center for Disease Control and Prevention (CDC) implemented environmental and human syndromic surveillance for the virus. Environmental samples from poultry markets in 21 city CDCs (n = 8,942) and respiratory samples from persons with influenza-like illness or pneumonia (n = 32,342) were tested; viruses isolated from 6 environmental samples and 16 patients were sequenced. Sequence analysis showed co-circulation of 4 influenza A(H7N9) virus strains that evolved by reassortment with avian influenza A(H9N2) viruses circulating in this region. In addition, an increase in human cases starting in late 2013 coincided with an increase in influenza A H7 virus isolates detected by environmental surveillance. Co-circulation of multiple avian influenza viruses that can infect humans highlights the need for increased surveillance of poultry and potential environmental sources.

Effect of Live Poultry Market Interventions on Influenza A(H7N9) Virus, Guangdong, China

“…All specimens from persons with suspected A(H7N9) infections were tested for subtypes H5, H7, and H9 as previously described ( 8 , 9 ). …”

“…Environmental samples were collected from LPMs in Guangdong Province during April 15, 2013–May 30, 2015 ( 8 – 10 ). Ten to 20 environmental samples per market were collected from selected markets in 21 prefecture-level cities.…”

The Third Wave: H7N9 Endemic Reassortant Viruses and Patient Clusters

“…Novel H7N9 variants were also detected in a number of cases in Guangdong, China [12][13][14]. New H7N9 variants contained internal gene segments PB1, PB2, NP, and NS, which were closely related to locally circulating H9N2 strains [12,13], revealing the potential for human infection with novel H7N9 reassortants circulating within the avian reservoir. Figure 2 shows a summary of H7N9 genotypic variants in eastern and southern China.…”

“…In addition to a geographic shift to southern China [2,9], the second H7N9 outbreak was associated with increased hospitalized patient fatality rates [10,11], including among individuals under 60 years of age [11]. Novel H7N9 variants were also detected in a number of cases in Guangdong, China [12][13][14]. New H7N9 variants contained internal gene segments PB1, PB2, NP, and NS, which were closely related to locally circulating H9N2 strains [12,13], revealing the potential for human infection with novel H7N9 reassortants circulating within the avian reservoir.…”

“…H9N2 viruses are endemic in the Chinese poultry population [16] and provide the opportunity for continual H7N9 reassortment and evolution, as evidenced by the new H7N9 variants detected in Guangdong during the second wave [12,13]. The dynamic nature of the H7N9 virus population has been further emphasized by phylogenetic analyses which have identified considerable genetic diversity among H7N9 viruses and ongoing internal gene segment exchange with enzootic H9N2 viruses [17,18].…”