Epidemiologic characterization of 30 confirmed cases of human infection with avian influenza A(H7N9) virus in Hangzhou, China

Abstract

BackgroundWe examined the clinical and epidemiological characteristics of 30 cases of human infection with avian influenza A(H7N9) virus in Hangzhou and investigated their external environments to provide evidence for contact tracing and disease prevention and control.MethodsThe cases confirmed from April 1 through May 1, 2013 were studied. Field epidemiologic surveys were conducted to collect the clinical and epidemiologic data. Case-related and environmental specimens were collected for etiologic detection.ResultsThirty cases of human infection with avian influenza A(H7N9) virus were confirmed in Hangzhou from April 1 through May 1, 2013, including one pregnant woman and three deaths. The median age of the patients was 62 years (range: 38–86 years). Twenty-three of the patients were men (76.67%). The median duration between disease onset and occurrence of respiratory failure and confirmed diagnosis was 5 and 6 days, respectively. Maximum medical observation of 666 close contacts of the patients revealed no irregularity. Of 314 external environmental specimens, the overall positive detection rate of H7N9 nucleic acid was 28.98%. Eight districts of Hangzhou city had positive detections in the external environments, the highest rate being in Yuhang District (78.13%). Statistical analysis of the specimen collection locations indicates a significant difference between the case-linked locations and the non-case locations (χ 2 = 16.563, p < 0.05) in terms of H7N9 viral nucleic acid detection rate. No epidemiologic link has been found among the 30 cases.ConclusionsMost of the infected were retired individuals aged 60 years or older. Men made the majority. The cases are sporadic at present, with no evidence of human-to-human transmission. Exposures to poultry and live poultry markets may be important sources of infection.

Factors associated with clinical outcome in 25 patients with avian influenza A (H7N9) infection in Guangzhou, China

“…These findings are consistent with those of other published reports. [ 9 , 10 , 26 , 27 ] The atypical symptoms recorded during the early stage of A (H7N9) patients were noteworthy. Two elderly patients were hospitalized due to neurological syndromes.…”

“…Fourteen patients (56 %) had died. This death rate was much higher than that of other areas, which ranged from 10 % in Hangzhou city [ 9 ] to 39.4 % in Shanghai [ 10 ]. This is of particular concern, as Guangzhou is a highly developed city in China with an advanced medical infrastructure, and the HA and NA sequences of the H7N9 viral isolates from Guangzhou patients are identical to those of H7N9 virus strains recently isolated from human patients in other areas (A/Anhui/1/2013, A/Shanghai/1/2013).…”

Pandemic potential of avian influenza A (H7N9) viruses

“…Interestingly, two-thirds of the infected individuals have been male 19, 20, 22–24, 27–29 (Figure 2C). The high number of cases among elderly men may reflect socio-economical differences among age groups and genders since elderly men may have frequent work-related or non-job-related contact with poultry.…”

The diversity of avian influenza virus subtypes in live poultry markets before and during the second wave of A(H7N9) infections in Hangzhou, China

“…It has been demonstrated that exposure to poultry in live poultry markets (LPMs) is strongly associated with human infections of avian influenza virus (AIV) subtype A(H7N9) 1 . In Hangzhou, the capital city of Zhejiang province, China, the first outbreak of human A(H7N9) infections emerged in April 2013 and was halted soon after the closure of LPMs in the main districts of the city 2 , 3 . These LPMs were reopened at the end of June 2013.…”