Introduction

Virology is the special branch of microbiology devoted to the study of viruses. Viruses are obligate intracellular parasites that infect both prokaryotic and eukaryotic cells. Outside their host cell, viruses exist as inert crystal particles (Crawford 2011) but remain infectious. The study of viruses started in the nineteenth century, with tobacco mosaic virus (TMV) being the first virus to be crystalised and characterised in 1935 (Pennazio 2010; Chaitanya 2019; Fauquet 2008). Viruses lack intracellular organelles essential for life, such as mitochondria, ribosomes, and replication machinery. Therefore, they cannot survive independently but depend on their host machinery for their basic life processes. For example, viruses use their host cell-generated nucleotides for replication and transcription and host ribosomes to translate their mRNA into proteins. They also lack an energy generation system; thus, they utilise energy from the host mitochondria for these processes. Viruses cannot generate or store ATP (Chaitanya 2019).