Coronaviruses are the largest positive strand of RNA virusesknown to the scientific world. They are known for affecting both animals andhuman beings and they commonly trigger different types of enteric andrespiratory disease. They belong to a certain group called nidovirales. Other typesof viruses which also belong to this group include the arteriviruses andtoroviruses. Arteriviruses are the only ones from the group which arecharacterized by icosahedral nucelocapsids, while the other ones have helicalnucleocapsids. The envelope of coronaviruses is derived from the intracellularmembrane, unlike most other viruses. When observed in electron micrographs,coronaviruses are characterized by tiny spikes which stick out of the viruses’surfaces. This is how the viruses got their name. There are also certain typesof sequenced coronaviruses and the most common one is the so called SARS virus.The structural order of the genes is always the same and the polymerase isalways at the 5’ end. It is closely followed by four distinct types of proteinswhich can be found in all different types of coronaviruses. These proteinsinclude the nucleocapsid protein, the membrane protein, the envelope proteinand the spike protein. In most cases the S protein which is the majorattachment one binds to sialic acid. There are certain types of the virus whichdo not bind to the cialic acid at all. The viral membranes fuse with thecellular membranes so that the virus can get further replicated in the cytoplasmof the cells. Each progeny virus contains several types of mutations, and thereare also a certain number of deletion mutations present in coronaviruses.
Colds and other Aspects of Coronavirus Disease Pathogenesis
Coronaviruses are held responsible for the onset of numerousdifferent types of enteric and respiratory disease which may affect bothanimals and human beings. The viruses usually replicate in the epithelial cellsof the respiratory tract. In fact, at least one third of all cases of colds aretriggered by certain types of coronaviruses. The symptoms of such medicalconditions are largely similar to those of colds triggered by rhinoviruses andthey include chills, fever, headache, cough, sore throat and runny nose, amongother. The incubation time of these viruses is usually no more than 3 days. Theimmune response limits the viral spread to a certain degree, but unfortunatelysuch activity is only short lived. The aforementioned symptoms may be presentfor several days and their severity may range from person to person, dependingon the individual case. Some cases may not involve any noticeable symptoms atall. The main difference between rhinoviruses and coronaviruses is thatcoronoviruses are unstable while the former ones are not enveloped. Theseviruses are transmitted by means of transfer of nasal secretions. When theepithelial cells of enteric tract get infected by the coronaviruses, theyusually lead to the occurrence of diarrhea. In most cases, these viruses arelocal but sometimes they can spread and be held responsible for infections of theinner ear, pneumonias and myocarditis. In most cases, coronaviruses can betreated quite successfully, but they are also characterized by frequentreinfection. Colds associated with coronaviruses are much more common duringthe winter because of closer contact involved. Most cases of coronavirusesinduced medical conditions are self limiting and there are a large number ofcases which go completely unnoticed or at least undiagnosed. The proper processof diagnosis involves serology and immune electron microscopy. The infectionsare commonly not treated by any prescribed medications, but a large number ofdifferent types of over the counter drugs can be of great help when it comes toalleviating the annoying symptoms.
Severe Acute Respiratory Syndrome (SARS)
SARS stands for severe acute respiratory syndrome. It is anew type of syndrome first observed in China in 2002. Nowadays it can bereported in other parts of the world as well. The most common types of symptomsassociated with this syndrome include a fever above 100.4 degrees Fahrenheit,aches, general malaise and headaches. In the initial stages of the conditionall the respiratory symptoms are commonly only mild, but after the course ofonly a few days the patient usually starts experiencing a dry and nonproductive cough which is also usually accompanied by difficulties inbreathing. There is a significant percentage of cases of the severe acuterespiratory syndrome which are associated with respiratory distress that endsup in death. Certain laboratory tests have shown that the severe acuterespiratory syndrome may be associated with reduced numbers of lymphocytes,increased aminotransferase activity and significant damage to the liver. Uptill now there have been more than 700 cases of death due to severe acuterespiratory syndrome. As of now there are no agreed treatment methods for thosewho suffer from the severe acute respiratory syndrome. There are no vaccinesagainst any known type of coronavirus.