MRC Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, Imperial College London, London, UK.
Influenza Other Respir Viruses. 2013 Sep;7 Suppl 2(Suppl 2):26-33. doi: 10.1111/irv.12077.
Highly pathogenic avian influenza A H5N1 viruses remain a significant health threat to humans given the continued rare occurrence of human cases with a high case fatality rate. This brief literature review summarizes available evidence of risk factors for H5N1 infection in humans and updates a recent systematic review published in early 2011. Several epidemiologic studies have been published to evaluate the risk factors for H5N1 infection in humans, including contact with poultry and poultry products and non-poultry-related contact such as from H5N1-contaminated water. While most H5N1 cases are attributed to exposure to sick poultry, it is unclear how many may be due to human-to-human transmission. The collective results of published literature suggest that transmission risk of H5N1 from poultry to humans may be highest among individuals who may have been in contact with the highest potential concentrations of virus shed by poultry. This suggests that there may be a threshold of virus concentration needed for effective transmission and that circulating H5N1 strains have not yet mutated to transmit readily from either poultry to human or from human to human. However, the mode of potential transmission can be quite varied throughout different countries and by study with exposures ranging from visiting a wet market, preparing infected poultry for consumption, to swimming or bathing in ponds frequented by poultry. Several important data gaps remain in the understanding of the epidemiology of H5N1 in humans and limit our ability to interpret the results of the available H5N1 seroepidemiologic studies.
高致病性禽流感 A(H5N1)病毒仍然是人类健康的重大威胁，因为人类感染病例罕见，但病死率却很高。本文献综述简要总结了人类感染 H5N1 的危险因素的现有证据，并更新了 2011 年初发表的最近的系统综述。已经发表了几项流行病学研究来评估人类感染 H5N1 的危险因素，包括与家禽和家禽产品的接触以及与非家禽相关的接触，如与 H5N1 污染的水的接触。虽然大多数 H5N1 病例归因于接触病禽，但尚不清楚有多少病例可能是由于人与人之间的传播。已发表文献的综合结果表明，H5N1 从家禽传播给人类的风险在与家禽接触可能具有最高潜在病毒浓度的个体中最高。这表明，对于有效传播，可能存在病毒浓度的阈值，而且循环的 H5N1 株尚未突变，无法从家禽轻易传播给人类，或从人类传播给人类。然而，在不同国家和通过研究，潜在的传播模式可能存在很大差异，这些研究的接触源从访问湿市场、准备受感染的家禽供食用，到在经常有家禽出没的池塘游泳或洗澡。在了解人类 H5N1 流行病学方面仍然存在一些重要的数据差距，限制了我们解释现有 H5N1 血清流行病学研究结果的能力。
