Comparative review of respiratory diseases caused by coronaviruses and influenza A viruses during epidemic season

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to sweep the world, causing infection of millions and death of hundreds of thousands. The respiratory disease that it caused, COVID-19 (stands for coronavirus disease in 2019), has similar clinical symptoms with other two CoV diseases, severe acute respiratory syndrome and Middle East respiratory syndrome (SARS and MERS), of which causative viruses are SARS-CoV and MERS-CoV, respectively. These three CoVs resulting diseases also share many clinical symptoms with other respiratory diseases caused by influenza A viruses (IAVs). Since both CoVs and IAVs are general pathogens responsible for seasonal cold, in the next few months, during the changing of seasons, clinicians and public heath may have to distinguish COVID-19 pneumonia from other kinds of viral pneumonia. This is a discussion and comparison of the virus structures, transmission characteristics, clinical symptoms, diagnosis, pathological changes, treatment and prevention of the two kinds of viruses, CoVs and IAVs. It hopes to provide information for practitioners in the medical field during the epidemic season.     

Molecular basis of the variability of epidemic strains of human influenza viruses

The data from literature and authors own studies are reviewed on variability of human influenza viral strains, isolated during the same epidemic season in different periods of pandemic cycle. The data obtained indicate that variability of epidemic strains of human influenza virus deals with the genes coding for outer membrane proteins (hemagglutinin and neuraminidase) as well as nonglycosylated proteins. Circulation of a number of viral variants of the same serotype, differing in antigenic specificity of outer membrane proteins or in the genes coding for nonglycosylated proteins was registered during one and the same season of one epidemic. During circulation of viral variants of the same serotype recombination may take place. Heterogeneity of viral strains circulating during different epidemic seasons of the same pandemic cycle is different. The possible mechanisms of development of the new epidemic variants of human influenza virus are discussed.     

Vaccinal prophylaxis of infarction, insult and lethality in the epidemic rise of influenza

The data of literature on the evaluation of the medical consequences of influenza and the role of vaccinal prophylaxis are presented and analyzed. The causes of differences in the characteristics of delayed lethality in influenza are noted. The fact was substantiated that delayed death in influenza may be essentially decreased if patients belonging to the group of risk (mainly persons over 65 years) were vaccinated before the beginning of the seasonal rise of infection. Vaccination against influenza was shown to decrease the frequency of hospitalization for pneumonia and influenza by 20-40%. In the group of vaccines the number of lethal outcomes due to infarctions and insults decreased by 48-50%, the risk of hospitalization for cardiovascular diseases decreased by 19% and that for disturbances of cerebral circulation, by 16%. The conclusion was made that the modern strategy of vaccination against influenza was aimed at the protection of the groups of risk and the prevention of complications appearing in the course of development of this infection (the exacerbation of chronic pathology, hospitalization, delayed death).     

Properties and dissemination of H5N1 viruses isolated during an influenza outbreak in migratory waterfowl in western China

H5N1 influenza A viruses are widely distributed among poultry in Asia, but until recently, only a limited number of wild birds were affected. During late April through June 2005, an outbreak of H5N1 virus infection occurred among wild birds at Qinghai Lake in China. Here, we describe the features of this outbreak. First identified in bar-headed geese, the disease soon spread to other avian species populating the lake. Sequence analysis of 15 viruses representing six avian species and collected at different times during the outbreak revealed four different H5N1 genotypes. Most of the isolates possessed lysine at position 627 in the PB2 protein, a residue known to be associated with virulence in mice and adaptation to humans. However, neither of the two index viruses possessed this residue. All of the viruses tested were pathogenic in mice, with the exception of one index virus. We also tested the replication of two viruses isolated during the Qinghai Lake outbreak and one unrelated duck H5N1 virus in rhesus macaques. The Qinghai Lake viruses did not replicate efficiently in these animals, producing no evidence of disease other than transient fever, while the duck virus replicated in multiple organs and caused symptoms of respiratory illness. Importantly, H5N1 viruses isolated in Mongolia, Russia, Inner Mongolia, and the Liaoning Province of China after August 2005 were genetically closely related to one of the genotypes isolated during the Qinghai outbreak, suggesting the dominant nature of this genotype and underscoring the need for worldwide intensive surveillance to minimize its devastating consequences.     

The epidemic spread of the influenza A and B viruses in the USSR in 1985-1986

The data on the spread of influenza A and B in the autumn and winter of 1985-1986 are given. Three epidemics caused by all presently circulating viruses, B, A (H3N2) and A (H1N1), were registered in the USSR. Of these, the greatest one was the epidemic of influenza B; morbidity rate among the adult population during this epidemic was at the level with the morbidity rate characteristic of the epidemics registered at the period of 1962-1972, and morbidity rate among children, especially school children, was even higher.     

Standards for laboratory diagnostics of legionellosis and their application during epidemic outbreak of pneumonia in town Verkhnyaya Pyshma

High effectiveness of application of international standards for legionellosis laboratory diagnostics was confirmed during investigation of pneumonia outbreak in town Verkhnyaya Pyshma. Use of immunochromatographic method and enzyme immunoassay for detection of Legionella antigen in urine of patients allows to confirm diagnosis of Legionella infection during several hours, promptly begin etiologic antibacterial treatment and reveal possible sources of infection in potentially dangerous environmental objects.     

Chikungunya epidemic outbreak in Emilia-Romagna (Italy) during summer 2007

During summer 2007, an outbreak due to the local transmission of CHIKV by Aedes albopictus mosquitoes occurred moreover in Italy, Emilia-Romagna Region, in the areas of Ravenna, Forli-Cesena, Rimini and Bologna cities. The original outbreak developed in Castiglione di Cervia and Castiglione di Ravenna, two small villages divided by a river. The first case was recorded on August 9th the epidemic outbreak then spread out, thus giving rise to smaller secondary outbreaks and further sporadic cases in the same area, for a total of 337 suspected cases, 217 of which confirmed by blood analysis. CHIKV has been isolated and characterized on both blood and mosquito samples.