禽流感的传播研究进展

从目前的疫情来看,H5N1亚型禽流感病毒尚未能形成持续的或社区人际传播能力,因此如何评估H5N1亚型禽流感病毒人-人传播能力、如何及时预警流行或大流行的到来成为了目前研究的热点.     

禽流感病毒实现种间传播的分子机制

近年来,H5、H7和H9亚型禽流感病毒跨越种间屏障不断感染人类,特别是人感染H5N1亚型高致病性禽流感后死亡率高达60％.然而这些毒株尚未获得有效的人传人能力,这可能源于人流感病毒和禽流感病毒受体结合特异性的差异,禽流感病毒必须适应人类受体才能实现人际间传播.因此,此文就病毒的氨基酸变异与受体结合特异性、病毒如何在哺乳动物间实现空气传播以及血凝素(HA)和神经氨酸酶(NA)之间功能平衡等方面对种间传播的影响作了综述.     

禽流感病毒跨种属感染及变异的分子流行病学研究

一般认为禽流感病毒(avian influenza virus,AIV)会较稳定的存在于野禽类,但是近几年来AIV不断使家禽类受到大面积感染,甚至打破种属屏障引起人或其他哺乳动物感染,且有些病例提示人_人传播的可能已经存在,这给世界公共卫生带来了严峻的考验。     

Probable tiger-to-tiger transmission of avian influenza H5N1

During the second outbreak of avian influenza H5N1 in Thailand, probable horizontal transmission among tigers was demonstrated in the tiger zoo. Sequencing and phylogenetic analysis of those viruses showed no differences from the first isolate obtained in January 2004. This finding has implications for influenza virus epidemiology and pathogenicity in mammals.     

禽流感病毒感染哺乳动物的致病机制

目前禽流感病毒(avian influenza virus,AIV)已跨越种属的限制,造成多种哺乳动物包括人在内的感染并导致死亡,但是关于AIV在人与人之间传播的证据很少。世界各国对此高度重视,并进行了大量研究工作。此文从AIV感染哺乳动物的临床特点、传播途径、组织病理学特征以及引起动物机体免疫应答等方面,对AIV感染哺乳动物的致病机制作了综述。     

Lack of H5N1 avian influenza transmission to hospital employees, Hanoi, 2004

To establish whether human-to-human transmission of influenza A H5N1 occurred in the healthcare setting in Vietnam, we conducted a cross-sectional seroprevalence survey among hospital employees exposed to 4 confirmed and 1 probable H5N1 case-patients or their clinical specimens. Eighty-three (95.4%) of 87 eligible employees completed a questionnaire and provided a serum sample, which was tested for antibodies to influenza A H5N1. Ninety-five percent reported exposure to > or = 1 H5N1 case-patients; 59 (72.0%) reported symptoms, and 2 (2.4%) fulfilled the definition for a possible H5N1 secondary case-patient. No study participants had detectable antibodies to influenza A H5N1. The data suggest that the H5N1 viruses responsible for human cases in Vietnam in January 2004 are not readily transmitted from person to person. However, influenza viruses are genetically variable, and transmissibility is difficult to predict. Therefore, persons providing care for H5N1 patients should continue to take measures to protect themselves.     

Detecting human-to-human transmission of avian influenza A (H5N1)

Highly pathogenic avian influenza A (HPAI) subtype H5N1 has caused family case clusters, mostly in Southeast Asia, that could be due to human-to-human transmission. Should this virus, or another zoonotic influenza virus, gain the ability of sustained human-to-human transmission, an influenza pandemic could result. We used statistical methods to test whether observed clusters of HPAI (H5N1) illnesses in families in northern Sumatra, Indonesia, and eastern Turkey were due to human-to-human transmission. Given that human-to-human transmission occurs, we estimate the infection secondary attack rates (SARs) and the local basic reproductive number, R0. We find statistical evidence of human-to-human transmission (p = 0.009) in Sumatra but not in Turkey (p = 0.114). For Sumatra, the estimated household SAR was 29% (95% confidence interval [CI] 15%-51%). The estimated lower limit on the local R0 was 1.14 (95% CI 0.61-2.14). Effective HPAI (H5N1) surveillance, containment response, and field evaluation are essential to monitor and contain potential pandemic strains.     

An introduction to avian and pandemic influenza

There are many types of influenza viruses, which cause illness in a variety of birds and mammals. New strains are constantly evolving, causing seasonal influenza epidemics in humans. This article provides information about influenza and influenza viruses, and the three influenza pandemics of the twentieth century. Pandemic influenza is differentiated from avian influenza, which is a viral disease that primarily infects birds. The current outbreak of avian influenza H5N1 in poultry flocks across the world is unprecedented in its spread. Human infection with avian influenza is rare and for most strains the symptoms are usually mild. A notable exception is HN51, where almost 60 per cent of the currently recorded 251 human cases have died. While the risk of a pandemic occurring in the current circumstances is unknown, there is a high level of concern worldwide.     

Apoptosis and pathogenesis of avian influenza A (H5N1) virus in humans

The pathogenesis of avian influenza A (H5N1) virus in humans has not been clearly elucidated. Apoptosis may also play an important role. We studied autopsy specimens from 2 patients who died of infection with this virus. Apoptosis was observed in alveolar epithelial cells, which is the major target cell type for the viral replication. Numerous apoptotic leukocytes were observed in the lung of a patient who died on day 6 of illness. Our data suggest that apoptosis may play a major role in the pathogenesis of influenza (H5N1) virus in humans by destroying alveolar epithelial cells. This pathogenesis causes pneumonia and destroys leukocytes, leading to leukopenia, which is a prominent clinical feature of influenza (H5N1) virus in humans. Whether observed apoptotic cells were a direct result of the viral replication or a consequence of an overactivation of the immune system requires further studies.     

Control of avian influenza in poultry

Avian influenza, listed by the World Organization for Animal Health (OIE), has become a disease of great importance for animal and human health. Several aspects of the disease lack scientific information, which has hampered the management of some recent crises. Millions of animals have died, and concern is growing over the loss of human lives and management of the pandemic potential. On the basis of data generated in recent outbreaks and in light of new OIE regulations and maintenance of animal welfare, we review the available control methods for avian influenza infections in poultry, from stamping out to prevention through emergency and prophylactic vaccination.     

WHO推荐禽流感应对临时措施

根据人类感染禽流感主要原因是接触了染病家禽及其粪便(或沾染了粪便的灰尘、泥土),采取临时防护措施如下：     

禽流感病毒对人类感染机制的研究进展

禽流感是由甲型流感病毒各亚型引起的禽类烈性传染病。由于病毒蛋白结构的差异 ,禽流感病毒具有严格的宿主限制性。自 1997年香港爆发禽流感后 ,不断有禽流感病毒感染人事件的发生。其感染人类的机制有 :病毒结合受体的改变、核蛋白PB2结构的改变和病毒自身核蛋白的基因重组。     

禽流感的威胁

禽流感(Avian influenza AI)过去相当一段时间内把它称之为鸡瘟(Fowl qlague)：它于1878年首次报道于意大利,1901年证实其病原为“滤过性”痫原体,1955年才证明其病原为甲型流感病毒的一员。后来发现实际上在禽中还有一种相似的疾病即新城疫(Newcastle disease ND)。常常两者混为一淡。为     

Interspecies transmission and limited persistence of low pathogenic avian influenza genomes among Alaska dabbling ducks

The reassortment and geographic distribution of low pathogenic avian influenza (LPAI) virus genes are well documented, but little is known about the persistence of intact LPAI genomes among species and locations. To examine persistence of entire LPAI genome constellations in Alaska, we calculated the genetic identities among 161 full-genome LPAI viruses isolated across 4 years from five species of duck: northern pintail (Anas acuta), mallard (Anas platyrhynchos), American green-winged teal (Anas crecca), northern shoveler (Anas clypeata) and American wigeon (Anas americana). Based on pairwise genetic distance, highly similar LPAI genomes (>99% identity) were observed within and between species and across a range of geographic distances (up to and >1000 km), but most often between isolates collected 0-10 km apart. Highly similar viruses were detected between years, suggesting inter-annual persistence, but these were rare in our data set with the majority occurring within 0-9 days of sampling. These results identify LPAI transmission pathways in the context of species, space and time, an initial perspective into the extent of regional virus distribution and persistence, and insight into why no completely Eurasian genomes have ever been detected in Alaska. Such information will be useful in forecasting the movement of foreign-origin avian influenza strains should they be introduced to North America.