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Environmental Variables in the Transmission of Respiratory Viruses
Published in Sunit K. Singh, Human Respiratory Viral Infections, 2014
Unlike in birds, influenza in horses is a primarily respiratory disease. Equine influenza A/H3N8 virus is highly infectious in all members of the family Equidae (including horses, donkeys, and zebras). It causes a severe but usually nonlethal respiratory illness that is similar in many clinical and epidemiological respects to human influenza.87,88 Wind-borne virus had been anecdotally associated with outbreaks of equine influenza among horse farms in South Africa and Jamaica in the 1980s; however, the introduction of equine influenza A/H3N8 to Australia in August 2007, where it had not previously been endemic, provided a discrete case study for more rigorous scientific analysis.88,89 Davis et al.89 investigated the pattern of spread of equine influenza that occurred among horse-holding properties between September and November 2007 in Park Ridge, a suburb of Brisbane, Queensland (27°S), on the east coast of Australia. Notably, a ban on the movement of horses had been instituted in Queensland on August 26, two weeks prior to the study period; thus, all transmission events after that date would have had to happen by indirect means (i.e., not direct horse-to-horse contact). The authors found that the vast majority of newly infected properties were within 1 km of the closest previously infected property, but not contiguous to it, eliminating the possibility of transmission between horses in adjacent pastures. Four significant space–time clusters of newly infected horses were identified, with each subsequent cluster arising to the south and/or west of the prior one. Although transfer of virus via people, birds, or other animals or insect species moving between properties cannot be completely excluded, the pattern of spread of the epizootic corresponded with the predominant easterly wind pattern, with average speeds of nearly 10 km/h. Interestingly, because this epizootic occurred in the Australian springtime, RH remained above 40% and daytime temperatures above 20°C for most of the study period,89 which is warmer and wetter than the conditions under which human seasonal influenza usually circulates in temperate zones,48 but which has been seen during human pandemics with antigenically novel influenza strains.75
An overview of advancement in aptasensors for influenza detection
Published in Expert Review of Molecular Diagnostics, 2022
Varsha Gautam, Ramesh Kumar, Vinod Kumar Jain, Suman Nagpal
It is perhaps another test for calibrating influenza typing recommended by WHO, with the principle being that the nucleic acids of viruses encode proteins, such as hemagglutinin, expressed on the viral surface [43]. Furthermore, HI assays have found wide use in the study of antigenic variations between strains in the surveillance of human influenza, i.e. allowing the identification of subtypes H3N8 and H7N7 of equine influenza. This also provides us knowledge of how much concentration of an antibody is present in the patient sample. The test is based on the influenza HA hemagglutination activity and the efficiency of HA specific antibodies to suppress the influenza virus by agglutinating the erythrocytes (Figure 5). These hemagglutinin proteins bind to or clump around erythrocytes to form a lattice that settles sporadically in the bottom of the test tube or microtiter well. The erythrocytes do not clump in the absence of viruses. Alternatively, forming a circular button. If antibodies against the suspected virus are present, the attachment of erythrocytes to viral protein hemagglutinin is inhibited. The results are expressed as hemagglutination titer, the highest dilution of serum that prevents hemagglutination. When there are no antibodies against the virus in the allantoic fluid, hemagglutination may occur in the wells diluted in sequence. A four-fold or greater rise in antibody titer from HI is considered evidence of infection. HI does not need cytopathy and doesn’t always occur in this assay for any influenza virus [44,45].