कोरोनाव्हायरस नवीन नाहीत; हे जगातील कोणत्याही गोष्टीइतके जुने आहेत आणि मानवांमध्ये अनेक वर्षांपासून सामान्य सर्दी होण्यासाठी ओळखले जातात. तथापि, त्याचे नवीनतम प्रकार, 'SARS-CoV-2' सध्या कारणांसाठी चर्चेत आहे Covid-19 महामारी नवीन आहे.
Often, common cold (caused by कोरोनाव्हायरस आणि इतर व्हायरस जसे की rhinoviruses) फ्लू सह गोंधळलेला आहे.
Flu and common cold, though both present similar symptoms are different in the sense that they are caused by different व्हायरस पूर्णपणे
फ्लू किंवा इन्फ्लूएंझा व्हायरस have a segmented genome which cause antigenic shift which occurs due to recombination among व्हायरस 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 व्हायरस accumulating mutations (change in its डीएनए structure) over a period of time that causes changes in the nature of surface proteins. All this makes it difficult to develop vaccine against them that could provide protection for long duration. The last pandemic of Spanish Flu of 1918 that killed millions of people was caused by flu or influenza व्हायरस. This is different from the coronaviruses.
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 कोरोनाविषाणू is normally limited to cold symptoms only and rarely made anyone seriously sick. However, there were some virulent forms of कोरोनाविषाणू 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 कोरोनाव्हायरस.
नवीनतम भिन्नता of कोरोनाव्हायरस, the novel कोरोनाव्हायरस (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 व्हायरस 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 कोरोनाव्हायरस reportedly underwent changes in its genome that made it into a highly virulent variant, responsible for the current pandemic.
पण SARS-CoV-2 इतका विषाणूजन्य आणि संसर्गजन्य बनवणारा इतका तीव्र प्रतिजैविक प्रवाह कशामुळे झाला असेल?
SARS-CoV-2 च्या उत्पत्तीकडे निर्देश करणारे अनेक सिद्धांत वैज्ञानिक समुदायात फिरत आहेत3,4. Proponents of man-made origin of the व्हायरस 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 कारण जर मानवाने निर्माण केले असेल व्हायरस 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 व्हायरस.
Be as it may, the fact of the matter remains that a certain almost innocuous व्हायरस 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 उत्क्रांती?
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संदर्भ:
- SARS-CoV-2 साठी Padron-Regalado E. लस: इतर कोरोनाव्हायरस स्ट्रेनचे धडे [मुद्रित करण्यापूर्वी ऑनलाइन प्रकाशित, 2020 एप्रिल 23]. संसर्ग डिस थेर. 2020;9(2):1-20. doi: https://doi.org/10.1007/s40121-020-00300-x
- लियांगशेंग झेड, फु-मिंग एस, फी सी, झेंगुओ एल. उत्पत्ति आणि उत्क्रांती 2019 कादंबरी कोरोनाव्हायरस, क्लिनिकल संक्रामक रोग, खंड 71, अंक 15, 1 ऑगस्ट 2020, पृष्ठे 882–883, DOI:https://doi.org/.1093/cid/ciaa112
- मोरेन्स DM, Breman JG, et al 2020. The Origin of Covid-19 आणि व्हाय इट मॅटर. अमेरिकन सोसायटी ऑफ ट्रॉपिकल मेडिसिन अँड हायजीन. ऑनलाइन उपलब्ध: 22 जुलै 2020. DOI: https://doi.org/10.4269/ajtmh.20-0849
- यॉर्क ए. कादंबरी कोरोनाव्हायरस वटवाघुळांपासून उड्डाण घेते? Nat Rev Microbiol 18, 191 (2020). DOI:https://doi.org/10.1038/s41579-020-0336-9
- अँडरसन केजी, रामबॉट, ए., लिपकिन, WI इत्यादी. SARS-CoV-2 चे प्रॉक्सिमल मूळ. नॅट मेड २६, ४५०–४५२ (२०२०). DOI: https://doi.org/10.1038/s41591-020-0820-9.
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