Family Clusters of Avian Influenza A H7N9 Virus Infection in Guangdong Province, China

Abstract

cSince its first identification, the epizootic avian influenza A H7N9 virus has continued to cause infections in China. Two waves were observed during this outbreak. No cases were reported from Guangdong Province during the first wave, but this province became one of the prime outbreak sites during the second wave. In order to identify the transmission potential of this continuously evolving infectious virus, our research group monitored all clusters of H7N9 infections during the second wave of the epidemic in Guangdong Province. Epidemiological, clinical, and virological data on these patients were collected and analyzed. Three family clusters including six cases of H7N9 infection were recorded. The virus caused severe disease in two adult patients but only mild symptoms for all four pediatric patients. All patients reported direct poultry or poultry market exposure history. Relevant environment samples collected according to their reported exposures tested H7N9 positive. Virus isolates from patients in the same cluster shared high sequence similarities. In conclusion, although continually evolving, the currently circulating H7N9 viruses in Guangdong Province have not yet demonstrated the capacity for efficient and sustained person-to-person transmission.

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

“…Such surveillance is difficult to implement because of a low infection rate and the absence of signs during A(H7N9) infection in poultry. However, most A(H7N9) infection in humans results from direct exposure to live poultry ( 25 ) (Technical Appendix Table 3). Furthermore, we used in our analyses environmental samples from LPMs, which partially reflect the circulation of avian influenza A strains in poultry.…”

Clinical severity of human infections with avian influenza A(H7N9) virus, China, 2013/14

“…Control of the virus in animals is complicated, because the infections in poultry are asymptomatic [11]. Human-to-human transmissibility of the virus remains limited, as evidenced by the very small number of potential secondary infections identified through detailed contact tracing of confirmed cases [1, 2, 12–14]. …”

The Third Wave: H7N9 Endemic Reassortant Viruses and Patient Clusters

“…This wave emerged in two principle locations, the Guangdong province of southern China and the Zhejiang province of eastern China [2,9,10]. The peak of the second wave coincided with the Chinese spring festival celebration of the lunar new year.…”

“…The clinical and epidemiologic features of human H7N9 infection may have changed during this second wave. 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].…”