**6. Continuous vigilance for variant of mutant strain of COVID 19 if any**

Recently, mutation of SarsCov2, namely N501Y, has been reported in the United Kingdom and linking it to further increased transmissibility. It is a matter of great concern, especially at a time when the emergence of vaccines has brought joy and expectation for the mass population. The new UK strain designated as VUI2020/12/01 (variant under investigation, year 2020, month 12, variant type 01) has recorded over 20 mutations, mostly silent, causing no change in the protein. Biologically, mutations represent steps in virus evolution under selection pressure of the host immunity. Scientists view these as a process evolved by the virus to escape immunity or to enhance transmissibility. As the virus replicates, mutations happen in its genes continually through a process called "antigenic drift", causing minor changes in the surface protein. However, changes of this kind could accumulate over time, and result in newer viruses that could become antigenically different such that the existing antibodies mounted by the host immune system to the original virus fail to recognise and neutralise them [30].

Scientists wish to have the answer about mechanism of these mutations and whether there is a role for host immunity in driving them? More importantly, could antibody treatment or other therapies have an influence in the process? The preprint of a recently submitted paper to medRxiv portal by the group in Cambridge, UK, led by Dr. Ravinder Gupta, has focused exactly on these issues [31]. The above study is based on a single case report of an immune compromised individual with chronic SARSCoV-2 infection, lasting over 100 days and treated with three units of convalescent plasma, two on day 65 and one on day 95 in an effort to neutralise the virus and treat the chronic infection. The virus was detectable in all his nasal swab samples collected at least 23 times over a period of 101 days, despite the plasma therapy. The authors investigated the SARS-CoV-2 evolution and found important changes in its genome caused by two new mutations in the spike protein, one a deletion of AA Histidine and Valine at positions 69 and 70 and, two, one AA replacement at position 796 (D796H). The authors state that while the two mutations did not increase infectivity of the virus, these might have been responsible for decreased sensitivity of the patient to convalescent therapy. Since it is a single case report, the results of the study is not generalizable. But, it raises an important issue of generation of "escape mutants" of the virus in patients with persistent infection. The virus escaped attack by neutralising antibodies present in the convalescent plasma. Continuous vigilance of such newer strains is needed particularly for both their transmissibility and potential to evade vaccine-mediated immunity. The emergence of new mutants of the coronavirus further emphasises the need for observing infection-control practices even more strictly and until the protective herd immunity is developed.

Epidemiologically, continuous collection of pertinent information is required to look for evolution of any variant or mutant strains over a period particularly with higher virulence and more destructing effect to human. Investigation facilities such as ability to perform genetic sequencing for matching newer strain with original virus is needed to identify them. It is obvious that earlier the detection, better actions to control the epidemic is possible. Finally, we wish to conclude that Ahmedabad COVID Control Model appears to be an important evidence in documenting the purpose of this chapter [32].
