The Source Of New Epidemic Viruses Biology Essay

This article is discoursing the ability of viruses to exchange hosts doing new epidemic diseases. The writer is proposing the beginning of some new viral diseases such as SARS and H5N1, the barriers that prevent some of them from being successful in altering hosts, their mechanism of development and version, the manner they transfer between different hosts, and the function of reassortment and recombination in assisting viruses to go more effectual upon infecting new hosts.

The writer suggests that the beginning of new epidemic viruses is old carnal viruses that infect domestic or wild animate beings. Unfortunately, we do non cognize a batch about them. This little fraction of cognition gave an advantage to viruses to convey between different species. One illustration is HIV/AIDS, which switched from a certain type of Chimpanzees to worlds. This viral switch, which took about 70 old ages ago infected 100s of 1000000s of people and caused between 1.8 to 4.1 million to decease yearly. Another illustration is SARS CoV which switched from chiropterans to worlds.

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It infected 1000s of people between 2002 and 2003, caused decease to 100s, and resulted in a entire loss of $ 40 billion dollars. Besides the writer included a tabular array incorporating a batch of viruses that switched hosts doing new epidemics. ( Table 1 ) .Then the writer discussed the barriers that alter the transmittal of the viruses between different hosts.

The first barrier is the strength of contact between the giver and the host. This is controlled by many factors such as demographics, geological, societal, and behavior separation between both giver and receiver. The more contact between the different species, the more opportunities for viruses to be introduced to new hosts. So the strength of contact is controlled by the size of the population of the receiver host. For illustration, human trade and travel helped in the transportation of a virus bearer called “ Aedes Albopictus mosquito ” and so exposing some viruses to new hosts.One thing that critically helps to increase the contact of carnal viruses with new hosts is “ intermediate and amplifying hosts. ” A virus, which usually has small contact with the new host, may infect an intermediate host that has closer contact with the new host so as to increase the opportunities for that virus to infect more hosts. The writer gave an illustration of Nipah virus epidemic in Malaysia.

The reservoir of that virus is Fruit Bats, which were attracted to pig farms due to the planting of fruit groves near these farms in Malaysia. This caused a spillover of the virus from the chiropterans ( less contact with worlds ) to pigs ( more contact with worlds ) , and magnifying the virus transmittal to worlds doing a large-scale eruption.The 2nd barrier is the host barriers. These barriers can be divided into many degrees get downing with the entry degree represented by the mucosal surface, and the unbroken tegument followed by the blood and lymphatic system.

The writer gave an illustration where the presence of glycans or lectins in the blood will demobilize most incursive viruses, e.g. Influenza viruses, because these viruses lack esterase or neuraminidase that are capable of destructing the glycans. Although worlds lack the glycans in their blood, the enteric bacterium has a sort of glycans called “ Galactosyl ( alpha1-3 ) brain sugar ” which elicits our defensive mechanisms to bring forth antibodies against it. So one time a virus is produced within our organic structure, it will be recognized quickly and destroyed by these antibodies.After that the virus needs to accommodate to the receptor adhering measure.

This measure demonstrates how specific the virus could be upon infecting other species. For illustration, SARS CoV is a virus that was derived from viruses that infect chiropterans. These viruses were found to respond otherwise with the ACE 2 receptor ( the receptor for SARS virus ) due to differences at a individual protein called “ S protein ” .

FIG 3B shows the construction of protein S, while the FIG 3A shows the fluctuation of protein S construction in 3 different SARS species: 2004 human epidemic, 2002 human epidemic, and palm civets SARS. One thenar civet virus out of 20 examined had a Therionine amino acid at the place 487, which is found in all 2002 human epidemic viruses. This could propose that both viruses are related and one of them switched into the other ‘s host. The avian and mammalian grippe viruses can adhere to different sialic acids or glycans linkages- which are found in the respiratory paths of worlds. This gives a great advantage for these influenza viruses to quickly accommodate to the new receptor in the new hosts. On the other manus, HIV-1 showed specificity to adhere to CD4 receptors and CCR5 or CXCR4 co-receptors. If these receptors/co-receptors are absent, this virus can non infect the host.The last host barrier could be some intracellular defence mechanisms against different facets of the viral life rhythm after entry.

The writer gave two illustrations. First, in instance of HIV-1 and SIV- like viruses which lack the appropriate Vif protein, the cell can pack cytidine deaminases into new virions so that they can non infect any new cells. Second, those viruses which depend on the mirid bug proteins for infection can be altered by the binding of TRIM5 alpha protein inside the cell to the infecting mirid bug protein doing the virus to disfunction.

Besides interferon plays a really of import function in the intracellular defence against viruses. For illustration, although murine noroviruses have a good ability for a broad scope receptor binding, it is restricted by alpha and beta interferon after entry.Afterwards, the writer discussed the viruses ‘ development through the evolutionary alterations to accommodate to the new host ‘s environment. The writer said that it is non necessary for the virus to hold evolutionary alterations in order to exchange hosts, nevertheless, in instance of limited host scope mutants and developments may play a critical function in assisting viruses to convey easy between hosts. An illustration of a virus that does non hold to mutate is laniary distemper virus which of course has a broad host scope and can infect many of the mammalian species in add-on to some Mariness. On the other manus, there are some viruses that are ill adapted to the new host and necessitate some evolutionary alterations to assist them to be better infectors. The writer suggested that in order for viruses to hold a better version ability they need to hold more familial fluctuation.

This leads to conclusion that RNA viruses should hold more capableness to accommodate to new hosts than Deoxyribonucleic acid viruses, because RNA viruses do non hold a proofreading mechanism and so they can non repair their errors. Besides, RNA viruses can retroflex faster than Deoxyribonucleic acid viruses. However, there is grounds that some RNA viruses ( hantaviruses and arenaviruses ) took a really long period of clip to accommodate to the new hosts.The writer stated that the mechanism of transmittal of viruses between hosts is non good understood yet, but there should be at least three hosts during a transmittal: the reservoir, the receiver, and the intermediate host ( vector ) .

The writer provided three suggested ways that the HIV virus was transmitted from Pan troglodytess to worlds ( FIG 5 ) . All of the three ways suggested that there was one or more intermediate between giver and receiver.Another suggestion provided by the writer for version is Recombination ( besides known as reassortment in viruses with metameric cistrons ) .

This could assist the familial fluctuation within the virus, leting it to hold more ability to accommodate to the new host. For illustration, H2N2 and H3N2 influenza A viruses were formed by the add-on of an avian genome into H1N1 virus. FIG 5 and FIG 4 besides show how HIV and SARS CoV could germinate due to recombination. On the other manus, the recombination procedure could cancel some of the cistrons coding for optimum protein constructions within viruses, forestalling them from being effectual.

For illustration, Influenza A virus has a composite for reproduction consisting of three proteins ( PA, PB1, PB2 ) . Reassortment could interrupt this composite, ensuing in less reproduction and hence less version.My Opinion:Although the article focused on the barriers and the troubles that could confront viruses in order to exchange to a new host, it did non give much information about the development of viruses and their mechanism of infection. The writer provided many solutions and schemes to forestall viruses from doing more epidemics and eruptions, but it would be much more effectual if we increased our concerns and surveies on animate being viruses, so we can contend that cross-transmission at the beginning point. The article was non interesting because most of the points suggested by the writer were “ non good understood ” .

Besides most of the surveies and tabular arraies provided were non illustrated expeditiously, which increased my confusion during reading.

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