Koronaviruset nuk janë të reja; këto janë aq të vjetra sa çdo gjë në botë dhe dihet se shkaktojnë ftohje të zakonshme tek njerëzit për shumë vite. Sidoqoftë, varianti i tij i fundit, 'SARS-CoV-2' aktualisht është në lajm për shkaktimin COVID-19 pandemia është e re.
Often, common cold (caused by koronavirus dhe të tjera viruset siç janë rinoviruset) ngatërrohet me gripin.
Gripi dhe ftohja e zakonshme, megjithëse të dyja paraqesin simptoma të ngjashme janë të ndryshme në kuptimin që ato shkaktohen nga viruse të ndryshme krejtësisht.
Flu or influenza viruses have a segmented genome which cause antigenic shift which occurs due to recombination among viruses of the same genus, thus changing the nature of the proteins on the viral surface responsible for generating immune response. This is further complicated by a phenomenon called antigenic drift which results from virus accumulating mutations (change in its ADN struktura) gjatë një periudhe kohore që shkakton ndryshime në natyrën e proteinave sipërfaqësore. E gjithë kjo e vështirëson zhvillimin e një vaksine kundër tyre që mund të sigurojë mbrojtje për një kohë të gjatë. Pandemia e fundit e gripit spanjoll të vitit 1918 që vrau miliona njerëz u shkaktua nga gripi ose virusi i gripit. Kjo është e ndryshme nga koronaviruset.
Coronaviruses, responsible for causing Common cold, on the other hand, do not possess a segmented genome hence there is no antigenic shift. They were minimally virulent and occasionally lead to death of the affected people. The virulence of koronaviruse is normally limited to cold symptoms only and rarely made anyone seriously sick. However, there were some virulent forms of koronaviruse in the recent past, namely SARS (Severe Acute Respiratory Syndrome) that appeared in 2002-03 in Southern China and caused 8096 cases, resulting in 774 deaths in 26 countries and MERS (Middle East Respiratory Syndrome) that appeared 9 years later in 2012 in Saudi Arabia and caused 2494 cases, resulting in 858 deaths in 27 countries1. However, this remained endemic and disappeared relatively quickly (within 4-6 months), possibly due to its less virulent nature and/or by following proper epidemiological procedures for containment. Hence, no need was felt at that time to invest heavily and develop a vaccine against such a koronavirus.
Fundit variant of koronavirus, the novel koronavirus (SARS-CoV-2) seems to be related to SARS and MERS2 which is highly infectious and virulent in humans. It was identified first in Wuhan China but soon became an epidemic and spread across the world to take the form of pandemic. Was this rapid spread across select geographies solely due to the high virulence and infectivity caused by changes in the genetic constitution of the virus or possibly due to lack of timely epidemiological intervention by reporting to the concerned national/transnational authorities which prevented timely containment measures, thereby causing about a million deaths so far and bringing the world economy to the grinding halt.
This is the first time in the human history that the existing koronavirus reportedly underwent changes in its genome that made it into a highly virulent variant, responsible for the current pandemic.
Por çfarë mund të ketë shkaktuar një zhvendosje kaq drastike antigjenike duke e bërë SARS-CoV-2 kaq virulent dhe infektiv?
Ka disa teori që qarkullojnë në komunitetin shkencor që tregojnë origjinën e SARS-CoV-23,4. Proponents of man-made origin of the virus believe that the genome changes seen in SARS-CoV-2 would take am extremely long period of time to develop naturally, while other studies argue that it may be of natural origin5 sepse nëse njerëzit do të krijonin virus artificially, why would they create a sub-optimal form that is virulent enough to cause a severe disease but binds sub-optimally to the human cells and the fact that it was not created using the backbone of the known virus.
Be as it may, the fact of the matter remains that a certain almost innocuous virus underwent genetic changes to transform itself to become mildly virulent SARS/MERS, and finally into a highly infectious and virulent form (SARS-CoV-2) in a span of 18-20 years, appears unusual. Such drastic antigenic drift, which incidentally has a continuum in between, would be highly unlikely to happen in a normal course, in the laboratory of Mother Earth, in such a short time duration. Even if it were to be true, what’s more perplexing is the environmental pressure that would have triggered such a selection in the evolucion?
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Referencat:
- Padron-Regalado E. Vaksinat për SARS-CoV-2: Mësime nga Shtamet e tjera të Koronavirusit [publikuar në internet përpara shtypjes, 2020 Prill 23]. Infekto Dis. 2020;9(2):1-20. doi: https://doi.org/10.1007/s40121-020-00300-x
- Liangsheng Z, Fu-ming S, Fei C, Zhenguo L. Origjina dhe Evolucioni i Novel Coronavirus 2019, Sëmundjet Klinike Infektive, Vëllimi 71, Botimi 15, 1 gusht 2020, Faqe 882–883, DOI:https://doi.org/.1093/cid/ciaa112
- Morens DM, Breman JG, et al 2020. Origjina e COVID-19 dhe Pse ka rëndësi. Shoqëria Amerikane e Mjekësisë Tropikale dhe Higjienës. E disponueshme në internet: 22 korrik 2020. DOI: https://doi.org/10.4269/ajtmh.20-0849
- York A. Koronavirusi i ri merr fluturimin nga lakuriqët? Nat Rev Microbiol 18, 191 (2020). DOI:https://doi.org/10.1038/s41579-020-0336-9
- Andersen KG, Rambaut, A., Lipkin, WI et al. Origjina proksimale e SARS-CoV-2. Nat Med 26, 450–452 (2020). DOI: https://doi.org/10.1038/s41591-020-0820-9.
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