One family cluster of avian influenza A(H7N9) virus infection in Shandong, China

Abstract

BackgroundThe first case of human infection with avian influenza A (H7N9) virus was identified in March, 2013 and the new H7N9 virus infected 134 patients and killed 45 people in China as of September 30, 2013. Family clusters with confirmed or suspected the new H7N9 virus infection were previously reported, but the family cluster of H7N9 virus infection in Shandong Province was first reported.Case presentationA 36-year-old man was admitted to Zaozhuang City Hospital with progressive respiratory distress and suspicion of impending acute respiratory distress syndrome on April 21. The chest radiography revealed bilateral ground-glass opacities and pulmonary lesions. The second case, the first case’s 4 year old son, was admitted to the same hospital on April 28 with fever and multiple patchy shadows in the bilateral lungs. Both of the two cases were confirmed to infect with H7N9 virus by the results of real-time reverse transcriptase-polymerase-chain reaction (rRT-PCR), virus isolation and serum antibody titer. At the same time, one environment samples was detected positive for H7N9 virus in the living poultry market in Zaozhuang. The homologous analysis of the full genome sequence indicated that both viruses from the patients were almost genetically identical. The field epidemiology investigation showed that the two cases had no recognized exposure to poultry, but had the exposure to the environment. The second case had substantial unprotected close exposure to his ill father and developed symptoms seven days after his last contact with his father. After surgery, the index case and his son were discharged on May 16 and May 6, respectively. 11 close contacts of both patients were identified and tested negative both the throat swabs and the serum antibody.ConclusionThe infection of the index case probably resulted from contact with environmentally contaminated material. For the son, the probable infection source was from the index case during unprotected exposure, but the possibility from the environment or other sources could not be completely ruled out.

Pandemic potential of avian influenza A (H7N9) viruses

“…Although sustained H7N9 virus transmission among humans has not been reported, the potential for human-to-human transmission cannot be ruled out in several family clusters 13, 27, 50, 51 . In some of these clusters, H7N9 infections occurred in blood-related family members, implying that close contacts in household settings, and perhaps also genetic factors, may be risk factors for infection with H7N9 viruses.…”

“…Most cases were reported from the provinces of Jiangsu, Zhejiang, and Shanghai, which are all located in the eastern part of China (Figures 1 and 2B). The detection of H7N9 viruses in live poultry markets 9–13 , and epidemiological data suggesting that contact with poultry or contaminated environments in live bird markets was the likely source of many (although not all) human cases (see ‘Epidemiology of human H7N9 virus infections’) prompted the Chinese government to close live poultry markets in several provinces in mid-April, 2013 14, 15 . This measure most likely led to the rapid decline in new human H7N9 cases during the following two weeks 16, 17 .…”

“…The following lines of evidence suggest that contact with live poultry is the source of human H7N9 virus infection: (i) most H7N9 patients had been exposed to live poultry prior to the onset of illness 10, 11, 19–21, 27–29, 31–33, 37–43 ; (ii) surveillance in live bird markets resulted in the isolation of H7N9 viruses with close homology to the H7N9 viruses isolated from humans in the same area 9–13, 41 ; (iii) a worker who had culled H7N9 virus-infected poultry developed a mild illness that was traced to a confirmed H7N9 virus infection 44 ; and (iv) serological surveillance of poultry workers in areas where human cases had been reported revealed antibodies to H7N9 viruses in >6% of the individuals tested, whereas no antibodies to H7N9 viruses were detected in the general population 45 . Collectively, these findings suggest an association between human H7N9 infections and poultry, likely in live bird markets, as underscored by the rapid decline in human H7N9 infections upon closure of these markets in mid-April, 2013 15–17 .…”

Prevention of nosocomial transmission of influenza A (H7N9) in Hong Kong

“…Person-to-person transmission of H7N9 has been reported among household contacts of infected patients. 1 To protect healthcare workers (HCWs) and hospital inpatients, an infection control preparedness strategy was established in our public health system, which includes active disease surveillance, early isolation of suspected cases, rapid molecular diagnostic testing, use of appropriate personal protective equipment (PPE) during patient care, and contact tracing for HCWs and hospitalized patients with unprotected exposure. 2 During influenza season HCWs are required to wear surgical masks during patient care, and N95 respirators and face shields when aerosol-generating procedures (AGPs) such as non-invasive positive pressure ventilation (BiPAP) and endotracheal intubation are performed.…”

Sialic Acid-Binding Protein Sp 2CBMTD Protects Mice against Lethal Challenge with Emerging Influenza A (H7N9) Virus

“…Overall, the case-fatality rate in humans is ϳ30%; however, H7N9 influenza viruses have low pathogenicity in domestic poultry and thus can spread silently. Although sporadic family clusters of H7N9 infection have been reported (2)(3)(4), there is no evidence of sustained human-to-human transmission (5). There remains the potential risk of acquiring additional mutations by H7N9 viruses or human coinfections with H7N9 and seasonal influenza viruses, which might lead to the genesis of viruses with greater human infection and transmission characteristics.…”