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Modes of Transmission of Coronavirus
Published in Ram Shringar Raw, Vishal Jain, Sanjoy Das, Meenakshi Sharma, Pandemic Detection and Analysis Through Smart Computing Technologies, 2022
Mohd. Faiz Saifi, Colin E. Evans, Neha Gupta
Another important factor determining the emergence of disease is the role of intermediate and amplifier hosts. They bring the animal virus in close contact with alternative hosts which would otherwise have little contact with the virus, e.g., for SARS-CoV, the virus is believed to have begun in bats and then spread to humans, civet cats, and other carnivores. Although the precise route of transmission is unknown, it is likely that infection of domesticated animals resulted in increased human exposure [58, 59]. Figure 1.4 represents the general outline of steps involved in viral host switching.
A Brief Introduction to Virology
Published in Rae-Ellen W. Kavey, Allison B. Kavey, Viral Pandemics, 2020
Rae-Ellen W. Kavey, Allison B. Kavey
The process of recombination identified by the Cold Springs Harbor team – two virus particles simultaneously infecting the same cell exchanging parts of their genetic material to produce new hybrid forms of the original viruses – was found to occur primarily in DNA viruses and was recognized as resulting in new viral strains which could infect previously resistant hosts, an important part of the infectivity of viruses. A particular form of recombination called “reassortment” occurred only in RNA viruses with segmented RNA, like the influenza virus. In this setting, whole segments of genetic material are exchanged, resulting in progeny with immediate and major antigenic change, a process called genetic shift.30 Based on findings like these, it was recognized that reassortment could yield an entirely new and antigenically novel virus strain. In the 30 minutes needed for a virus replication cycle, an infinitesimal killer virus could emerge, highly infectious, easily transmittable and lethal. It was molecular genetic work that identified this most important characteristic of RNA viruses: endless evolution by both spontaneous mutation and by genetic reassortment leading to continuous emergence of new, antigenically novel strains. Faced with an entirely new virus strain, human hosts have little if any resistance, so these emerging strains have high infectivity. This is especially true when reassortment occurs between an animal virus and a human virus.
Introduction to virus structure, classification, replication, and hosts
Published in Avindra Nath, Joseph R. Berger, Clinical Neurovirology, 2020
Philippe Simon, Kevin M. Coombs
As indicated earlier, there currently are more than 3600 known virus species. Viruses have been detected within every other type of living organism, from bacteria to plants and animals [20]. Some families of viruses are capable of infecting organisms from diverse kingdoms. For example, Rhabdoviridae are capable of infecting plants and animals. However, any given species of virus is usually extremely limited in the types of host cells it can infect. This is known as cell tropism. Thus, a particular virus capable of infecting some bacteria usually cannot infect all bacteria and also cannot infect any plants or animals. Most plant viruses are capable of infecting some, but not all, species of plants but cannot infect any bacteria or animals. Likewise, the cell tropism of a specific animal virus limits the capacity of the virus to infect only certain species of animals.
Next generation live-attenuated influenza vaccine platforms
Published in Expert Review of Vaccines, 2022
Generally, influenza virus vaccine production takes around 4–5 months [44]. Due to antigenic evolution in influenza viruses, strategies to incorporate attenuation into the internal gene segments have been adopted. To create MDV, gene segments other than HA and NA are targeted for attenuation. To generate an antigenically matched vaccine for the seasonal outbreak, MDV is paired with HA and NA genes [45]. Many temperature-sensitive (ts) viruses were evaluated as vaccine candidates [46]. Due to a small number of mutations, phenotypic reversion occurred in vaccine candidates, and therefore, only the ts strategy did not succeed [47,48]. Another approach involved was the use of animal viruses through the intranasal route. This approach showed a low level of virus replication in humans due to animal virus inability to replicate efficiently [49]. Due to avian viruses’ adaptation to humans, they were considered naturally attenuated in humans. Unlike previous studies with ts variants, the virus would not undergo loss of attenuation or phenotype reversion [45].
Functionalized selenium nanoparticles enhance the anti-EV71 activity of oseltamivir in human astrocytoma cell model
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2019
Jiayu Zhong, Yu Xia, Liang Hua, Xiaomin Liu, Misi Xiao, Tiantian Xu, Bing Zhu, Hong Cao
The regulation of cells apoptosis is a common characteristic of animal virus infection, and it also contributes to the pathogenesis process. Many animal viruses including EV71 were reported to induce host cells apoptosis [29]. The apoptotic cells percentages of U251 cells after EV71 infection were quantitatively analyzed by flow cytometry. As shown in Figure 6(A), the percentage of the apoptotic cell was dramatically elevated from 4.37% (uninfected control group) to 67.7% (EV71-infected group). After oseltamivir-, SeNPs- and SeNPs@OT-treatment, the apoptotic cell population of U251 cells were obviously decreased to 48.4, 57.4 and 26.8%, respectively, indicating that SeNPs@OT exhibited the strongest antivirus ability in EV71-infected U251 cells. These results revealed that SeNPs@OT could heighten the antivirus ability of oseltamivir to prevent U251 cells from apoptosis by loading oseltamivir onto the surface of SeNPs.
Ten challenging questions about SARS-CoV-2 and COVID-19
Published in Expert Review of Respiratory Medicine, 2020
Majid Teymoori-Rad, Saeed Samadizadeh, Alijan Tabarraei, Abdolvahab Moradi, Mahsa Bataghva Shahbaz, Alireza Tahamtan
Since the identification of the virus in late December 2019, there has been a considerable challenge within scientists, politicians, and communities about the origin of SARS-CoV-2. Several scenarios have been proposed to the origin of the virus. Some studies focused on zoonotic origin [1], some believed it is an inadvertent laboratory release, while others mentioned this virus is a purposefully manipulated laboratory construct. Indeed, an animal reservoir for some human coronaviruses such as SARS-CoV and MERS-CoV has been well accepted by several evolutional studies [2–4]. Full genome phylogenetic analysis, which emphasized closely related to bat SARS-like CoV (about 88%) and partially similar to the SARS-CoV (about 79%) and MERS-CoV (about 50%), appears to support this notion [5,6]. Several studies have also shown that SARS-CoV-2 has high sequence homology to the Guangdong pangolin coronaviruses (˃99%) in the receptor-binding domain, which indicates pangolins can be either the source or an intermediate host for the virus before transmission to humans [7]. Although there are limited data regarding the possibility of an inadvertent laboratory release of SARS-CoV-2, the comparative analysis of genomic data clearly showed that SARS-CoV-2 is not a laboratory construct or a purposefully manipulated virus [8]. In the recent published study, two scenarios to explain the zoonotic origin of SARS-CoV-2 were investigated: (i) natural selection in the animal source before transmission to humans; and (ii) natural selection in humans following transmission [8]. Given the fact that the ability of transmission to human and spread among human society for an animal virus need a long journey and time, the manner of zoonotic transfer and adaptation process in humans has not fully defined yet.