禽流感与禽流感病毒研究进展

对禽流感的症状、传播、感染、流行规律、疾病发生历史、流行监测、诊断、防治以及禽流感病毒的分类地位、命名、病毒粒子形态结构、病毒基因组结构、病毒复制、病毒变异的研究进展作了综合评述,并对该领域的研究热点和方向作了探讨。     

Endocytosis of influenza viruses

Receptor-mediated endocytosis is known to play an important role in the entry of many viruses into host cells. However, the exact internalization mechanism has, until recently, remained poorly understood for many medically important viruses, including influenza. Developments in real-time imaging of single viruses as well as the use of dominant-negative mutants to selectively block specific endocytic pathways have improved our understanding of the influenza infection process.     

Genesis of pandemic influenza

During the last decade the number of reported outbreaks caused by highly pathogenic avian influenza (HPAI) in domestic poultry has drastically increased. At the same time, low pathogenic avian influenza (LPAI) strains, such as H9N2 in many parts of the Middle East and Asia and H6N2 in live bird markets in California, have become endemic. Each AI outbreak brings the concomitant possibility of poultry-to-human transmission. Indeed, human illness and death have resulted from such occasional transmissions with highly pathogenic avian H7N7 and H5N1 viruses while avian H9N2 viruses have been isolated from individuals with mild influenza. The transmission of avian influenza directly from poultry to humans has brought a sense of urgency in terms of understanding the mechanisms that lead to interspecies transmission of influenza. Domestic poultry species have been previously overlooked as potential intermediate hosts in the generation of influenza viruses with the capacity to infect humans. In this review, we will discuss molecular and epidemiological aspects that have led to the recurrent emergence of avian influenza strains with pandemic potential, with a particular emphasis on the current Asian H5N1 viruses.     

Highly pathogenic avian influenza virus inducing influenza pneumonia in humans

The human disease caused by avian influenza virus in South Asia is a typical example of emerging infection resulting from transmission of a known causative agent to a new host. The first cases with a comparatively high level of lethality rates among patients were registered in 1997 and 1999. The situation is a special phenomenon in epidemiology which requires deep evolutionary and ecological analysis, as well as theoretical interpretation. With the example of avian influenza virus in Western Europe and South Asia in 2003-2004 the practical expediency of modern concepts "foci versus epidemics" and "eradication versus vaccination" is now evident.     

Avian influenza virus

Recent outbreaks of highly pathogenic avian influenza in chickens and ducks that occurred in 9 Asian countries including Japan alarmed to realize that there is no border for infections and gave a rise to great concern for human health as well as for agriculture. This H5N1 virus jumped the species barrier and caused severe disease with high mortality in humans in Viet Nam and Thailand; 15 deaths of 22 cases and 8 of 12, respectively. A second concern was the possibility that the situation could give rise to another influenza pandemic in humans since genetic reassortment may occur between avian and human influenza viruses when a person is concurrently infected with viruses from both species. This process of gene swapping inside the human body can give rise to a new subtype of the influenza virus to which humans would not have immunity. The outbreaks also emphasized the need to continue active surveillance on avian influenza throughout the year to undertake aggressive emergency control measures as soon as an infection is detected.