Probable person-to-person transmission of avian influenza A (H5N1).
ABSTRACT During 2004, a highly pathogenic avian influenza A (H5N1) virus caused poultry disease in eight Asian countries and infected at least 44 persons, killing 32; most of these persons had had close contact with poultry. No evidence of efficient person-to-person transmission has yet been reported. We investigated possible person-to-person transmission in a family cluster of the disease in Thailand.
For each of the three involved patients, we reviewed the circumstances and timing of exposures to poultry and to other ill persons. Field teams isolated and treated the surviving patient, instituted active surveillance for disease and prophylaxis among exposed contacts, and culled the remaining poultry surrounding the affected village. Specimens from family members were tested by viral culture, microneutralization serologic analysis, immunohistochemical assay, reverse-transcriptase-polymerase-chain-reaction (RT-PCR) analysis, and genetic sequencing.
The index patient became ill three to four days after her last exposure to dying household chickens. Her mother came from a distant city to care for her in the hospital, had no recognized exposure to poultry, and died from pneumonia after providing 16 to 18 hours of unprotected nursing care. The aunt also provided unprotected nursing care; she had fever five days after the mother first had fever, followed by pneumonia seven days later. Autopsy tissue from the mother and nasopharyngeal and throat swabs from the aunt were positive for influenza A (H5N1) by RT-PCR. No additional chains of transmission were identified, and sequencing of the viral genes identified no change in the receptor-binding site of hemagglutinin or other key features of the virus. The sequences of all eight viral gene segments clustered closely with other H5N1 sequences from recent avian isolates in Thailand.
Disease in the mother and aunt probably resulted from person-to-person transmission of this lethal avian influenzavirus during unprotected exposure to the critically ill index patient.
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ABSTRACT: A wide range of influenza A viruses of pigs and birds have infected humans in the last decade, sometimes with severe clinical consequences. Each of these so-called zoonotic infections provides an opportunity for virus adaptation to the new host. Fortunately, most of these human infections do not yield viruses with the ability of sustained human-to-human transmission. However, animal influenza viruses have acquired the ability of sustained transmission between humans to cause pandemics on rare occasions in the past, and therefore, influenza virus zoonoses continue to represent threats to public health. Numerous recent studies have shed new light on the mechanisms of adaptation and transmission of avian and swine influenza A viruses in mammals. In particular, several studies provided insights into the genetic and phenotypic traits of influenza A viruses that may determine airborne transmission. Here, we summarize recent studies on molecular determinants of virulence and adaptation of animal influenza A virus and discuss the phenotypic traits associated with airborne transmission of newly emerging influenza A viruses. Increased understanding of the determinants and mechanisms of virulence and transmission may aid in assessing the risks posed by animal influenza viruses to human health, and preparedness for such risks.02/2014; 3(2):e9. DOI:10.1038/emi.2014.9
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ABSTRACT: The avian influenza A H7N9 virus, previously unknown in humans, has infected humans in many areas of China since February 2013. Here we report on a clustering case of H7N9 in two little girls in one family in Dongyang city, Jinhua area, Zhejiang Province. To determine (1) whether the infections were due to person-to-person transmission or to co-exposure to poultry and (2) the prevalence of this novel H7N9 virus in Dongyang inferred by this family clustering case. Samples were collected from patients and environment. We undertook detailed epidemiological investigations and laboratory work. Phylogenetic analyses were done based on the sequenced genomes. The concentration of cytokines and chemokines in the serum was detected by cytometric bead array analyses. A mixture of H7 and H9 was detected from the environmental sample. The three H7N9 viruses shared one infection source. The index patient who had significantly higher levels of IL-4, IL-8 and IL-10 suffered severe infection. Based on a comparison with previous isolations of the virus in 2013, H7N9 has evolved different lineages through recombination with local H9N2 viruses. Determining whether it was human-to-human transmission or exposure to the same live poultry, since both patients had identical exposure histories, was ambiguous. The results from the cytokine analyses agreed with the conclusion that H7N9 severity is associated with a higher level of cytokines/chemokines. Long term influenza surveillance remains essential to allow for early warning of potential transmission events. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.Journal of clinical virology: the official publication of the Pan American Society for Clinical Virology 02/2015; 63:18-24. DOI:10.1016/j.jcv.2014.11.034 · 3.47 Impact Factor
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ABSTRACT: Incorporation of 'social' variables into epidemiological models remains a challenge. Too much detail and models cease to be useful; too little and the very notion of infection - a highly social process in human populations - may be considered with little reference to the social. The French sociologist Émile Durkheim proposed that the scientific study of society required identification and study of 'social currents'. Such 'currents' are what we might today describe as 'emergent properties', specifiable variables appertaining to individuals and groups, which represent the perspectives of social actors as they experience the environment in which they live their lives. Here we review the ways in which one particular emergent property, hope, relevant to a range of epidemiological situations, might be used in epidemiological modelling of infectious diseases in human populations. We also indicate how such an approach might be extended to include a range of other potential emergent properties to represent complex social and economic processes bearing on infectious disease transmission.Global Public Health 02/2015; 10(4):1-11. DOI:10.1080/17441692.2015.1007155 · 0.92 Impact Factor