Influenza virus research paper The Pathology of Influenza Virus Infections

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Epithelium of the bronchioli Changes in the smaller airways are similar to those described above for larger airways.

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A and B type viruses contain eight discrete gene segments, each of them coding for at least one protein. Although the clinical course was usually self-limiting, a substantially higher percentage of cases developed severe pneumonic complications. Tracheobronchial Changes in Influenza Starting with the first pathological studies of influenza associated with the pandemic 156869involvement scandinavian airlines system sas case study epithelial cells lining the upper respiratory tract has influenza virus research paper universally recognized and corresponds to the clinical signs and symptoms of pharyngitis and tracheobronchitis.

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Opie et al. Because of the simpler structure of the bronchiolar epithelium, thinning and flattening of these cells can be more pronounced than in the larger airways.

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After reemergence inthe essay uses of electricity H5N1 HPAI epizootic continued to produce spillover infections in humans, causing concern that adaptation of this virus to humans could cause a pandemic Common changes include focal epithelial necrosis to necrosis of the entire wall, peribronchial hemorrhage, and peribronchial pneumonia.

At autopsy, the almost constant coexistence of secondary bacterial infections of the air passages in fatal interpandemic and pandemic influenza complicates the picture, making it difficult to ascribe observed changes solely to influenza virus infection.

H2N2 viruses circulated until when replaced by H3N2viruses of the pandemic.

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Although one of the absolute requirements for a pandemic is that HA must change, the extent to which the rest of the virus can or must change is not known. Air spaces may be filled with edema, fibrin, and varying numbers of neutrophils The HA molecule initiates infection by binding to receptors on specific host cells.

The Pathology of Influenza Virus Infections Influenza A viruses, however, infect a wide variety of warm-blooded animals, including birds, swine, horses, humans, and other mammals.

Their findings reiterate pathologic changes observed in and are concordant with the smaller number of influenza pathology studies published in recent decades. The lumina contained large amounts of frothy blood-stained material. The large number of autopsy studies reported during and after the influenza pandemic all report such changes, particularly severe tracheitis.

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The virus was recently completely sequenced using archevirologic techniques in which reverse-transcriptase polymerase chain reaction RT-PCR for small fragments of viral RNA were analyzed from lung tissues of influenza victims 52 — Inthe HA and PB1 genes were similarly replaced 50 The three virus types differ in host range and pathogenicity. Several case clusters of H5N1 infections have been reported A neutrophilic exudate may be present in the bronchiolar lumen.

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  2. Grossly, in early cases, the epithelial linings are erythematous and filled with thin blood-stained froth or fluid.
  3. The more recently developed neuraminidase NA inhibitors, zanamivir and oseltamivir, are effective against both influenza A and B viruses.
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  5. Antibodies against the HA protein prevent receptor binding and are effective at preventing re-infection with the same strain.
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Inthree genes from the circulating H1N1 human influenza virus were replaced by avian-like genes: As histologic changes are nonspecific, histologic analysis alone is insufficient to make a specific diagnosis 19 ; diagnosis typically requires supporting diagnostic tests such as viral isolation, rapid diagnostic tests including RT-PCRserologic studies, or a biopsy or autopsy tissue section confirmed by in situ hybridization or hardware support cover letter techniques The final stage of desquamation of the affected epithelium frequently shows only a single layer of flattened basalar epithelial cells covering the basement membrane.

InH1N1 strains from the pre period reappeared, and since then both influenza A subtypes H3N2 and H1N1 have co-circulated in humans RT-PCR reverse-transcriptase polymerase chain reaction The pandemic was the most lethal influenza pandemic on record.

Often only a basal layer of the epithelium remains.

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Matrix 2 ion channel blockers amantadine and rimantadine are effective against influenza A viruses, but resistant viral strains develop rapidly and have been recognized in approximately one-third of treated patients. Biology of Influenza Viruses Influenza viruses of the family Orthomyx-oviridae are enveloped negative-strand RNA viruses with segmented genomes containing seven to eight gene segments Influenza A viruses, however, infect a wide variety of warm-blooded animals, including birds, swine, horses, humans, and other mammals.

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Influenza C viruses have seven segments and only one surface glycoprotein An outstanding feature in early stages of infection is the absence of neutrophils in the infiltrate, but as epithelial cell necrosis occurs, these cells migrate in.

Mutations that change amino acids in the antigenic portions of surface glycoproteins may produce selective advantages for viral strains by allowing them to evade preexisting immunity.

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Influenza A viruses are subdivided by antigenic characterization of the hemagglutinin HA and NA surface glycoproteins that project from the virion. The more recently developed neuraminidase NA inhibitors, zanamivir and oseltamivir, are effective against both influenza A and B viruses.

Scandinavian airlines system sas case study later stages, Askanazy observed evidence of epithelial regeneration with the formation of a nonkeratinizing stratified squamous metaplasia in 38 of 90 cases Type B and C influenza viruses are isolated almost exclusively from humans, although influenza B viruses have been isolated from seals and influenza C viruses have been isolated from pigs and dogs 44 This review concentrates on the pathology of the lower respiratory tract.

The interstitium may show congestion, edema, and an inflammatory infiltrate. The trachea and bronchi had markedly reddened and swollen mucosal surfaces, sometimes overlaid with mucopurulent material.

Sixteen HA subtypes are known to exist in wild birds and provide a source of HAs novel to humans 46 The emergence in human circulation of an influenza strain with a novel subtype by antigenic shift has been the cause of the past influenza virus research paper influenza pandemics in and ; in both cases, the previously circulating postpandemic human virus imported an HA from an unidentified avian or avian-like virus Edema and congestion of the submucosa are often marked Moreover, mortality during the pandemic was concentrated in an unusually young age group 6.

They were among the only observers of the pandemic to reach such a conclusion Influenza A and B viruses suicide research paper title a similar structure, whereas influenza C is more divergent.

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Winternitz et al. As a result, the case mortality rate in the United States averaged 2.

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These changes were carefully described by several distinguished pathologists in the aftermath of the influenza 2070 — Its descendants circulated in humans until when they were replaced by an H2N2 subtype pandemic strain. Before the epizootic was contained, at least 86 poultry workers and three contacts had been infected and developed conjunctivitis with or without an ILI.

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Necrotic cells may also undergo phagocytosis by macrophages. For example, in the exposure of a limited number of soldiers to a swine-adapted H1N1 influenza virus in Fort Dix, New Jersey, there was one death 60 Lucke et al.

In later cases, the epithelia are necrotic. Age-specific morbidity was similar to other pandemics, with children under 15 years of age experiencing the highest rates of infection For example, strains included in the most recent trivalent vaccine for the — season in the United States were: They noted submucosal capillary congestion and thrombi and found that the bronchiolar wall was sometimes entirely necrotic and associated with a polymorphonuclear cell infiltrate.

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Although epidemiologic information has been limited, person-to-person transmission of H5N1 has been suggested in a few instances, usually involving family members. Goodpasture 75 described the pathology of small- and medium-sized bronchioles in Annual revaccination is thus recommended for those at high risk.

Both classes of drugs are effective in preventing influenza when administered prophylactically 37 — The reasons for these unexpected patterns remain obscure. The HA and NA can evade previously acquired immunity by either a antigenic drift, in which mutations limit or prevent antibody binding, or b antigenic shift, in which the virus acquires HA of a new subtype by reassortment between two influenza A viruses 2.

Antiviral drugs can have both therapeutic and prophylactic effects, but to prevent disease they must be administered continuously at times of high influenza activity.

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Winternitz and his homework ko, however, clearly recognized that the epithelium of the trachea, bronchi, and the pulmonary alveoli were primary sites of influenza viral replication. These structural changes to the epithelium are often irregularly distributed, introduction of an essay about extracurricular activities regions of pathology can abut areas appearing histologically normal.

Complete loss of the epithelial layer can be seen kitchen hygiene homework answers ciliated and goblet cellsoften associated with the formation of hyaline membranes at these sites.

Such surveillance is the cornerstone of the World Health Organization influenza surveillance network