Avian Influenza Virus Tropism in Humans

Abstract

An influenza pandemic happens when a novel influenza A virus is able to infect and transmit efficiently to a new, distinct host species. Although the exact timing of pandemics is uncertain, it is known that both viral and host factors play a role in their emergence. Species-specific interactions between the virus and the host cell determine the virus tropism, including binding and entering cells, replicating the viral RNA genome within the host cell nucleus, assembling, maturing and releasing the virus to neighboring cells, tissues or organs before transmitting it between individuals. The influenza A virus has a vast and antigenically varied reservoir. In wild aquatic birds, the infection is typically asymptomatic. Avian influenza virus (AIV) can cross into new species, and occasionally it can acquire the ability to transmit from human to human. A pandemic might occur if a new influenza virus acquires enough adaptive mutations to maintain transmission between people. This review highlights the key determinants AIV must achieve to initiate a human pandemic and describes how AIV mutates to establish tropism and stable human adaptation. Understanding the tropism of AIV may be crucial in preventing virus transmission in humans and may help the design of vaccines, antivirals and therapeutic agents against the virus.

Humoral Immunity to Influenza Infection among the Russian Population

“…In addition, low herd immunity to seasonal influenza increases the risk of the emergence of viral variants with a pandemic potential. Experts believe two main mechanisms to be involved in the emergence of pandemic viruses: reassortment of human and animal influenza virus genomes; and /or gradual adaptation to a new host [3,10]. Any mechanism for the emergence of pandemic viral variants includes a pre-pandemic period, necessary for the virus to adapt optimally to humans.…”

“…Since people have no immunity to such variants, the latter may cause an outbreak of the disease. However, in order to become pandemic viruses, effectively infect and spread from person to person, these viruses require further adaptation to a new host [3]. This process is difficult to track, since new intermediate viral variants may not cause severe human disease and remain unnoticed for a long time.…”

Recommendations for the management of children with influenza in a primary care setting – COMPAS INFLUENZA. Update for the 2023/2024 season

“…Human infections caused by influenza A and B are clinically important; type C is of less epidemiological importance. Influenza A and B are composed of a genome (segmented, single-stranded, negative-sense RNA), a protein capsid with antigenic proteins, neuraminidase (NA) and haemagglutinin (HA), on its surface, and a lipoprotein envelope (3) . • Influenza A has many subtypes, which are distinguished based on the HA (subtypes H1 to H18) and NA (subtypes N1 to N11) antigenic properties.…”

“…• Influenza B contains only one type of HA and NA in its structure, originating from two cell lineages: Yamagata or Victoria. Influenza B usually causes milder infections than those caused by influenza A (1,3) . Influenza B viruses show high genetic stability.…”

Cellular receptors for mammalian viruses

“…There are numerous examples showing the evolution of key mutations in viral receptor-binding proteins that promote transmissibility. For instance, certain changes in the influenza virus hemagglutinin determine sialic acid preferences and the ability of avian strains to infect humans [5,6]. Similarly, changes in the affinity of the viral spike protein for human ACE2 have been instrumental in the emergence and evolution of SARS-CoV-2 [7,8].…”