Virus

• A virus is a tiny, infectious particle that can reproduce only by infecting a host cell.
• Viruses "commandeer" the host cell and use its resources to make more viruses, reprogramming it to become a virus factory.
• Viruses are obligate cellular parasites, meaning they can't reproduce without a host.
• Viruses are basically just packages of nucleic acid and protein.
• Viruses have nucleic acid genomes that have genetic variation and can evolve.
• The renin–angiotensin–aldosterone system (RAAS) is a cascade of vasoactive peptides that orchestrate key processes in human physiology.
• The interaction between the SARS viruses and ACE2 has been proposed as a potential factor in their infectivity and there are concerns about the use of RAAS inhibitors that may alter ACE2 and whether variation in ACE2 expression may be in part responsible for disease virulence in the ongoing Covid-19 pandemic.
• Population-based studies have estimated that only 30 to 40% of patients in China who have hypertension are treated with any antihypertensive therapy; RAAS inhibitors are used alone or in combination in 25 to 30% of these treated patients.
• The capsid or protein shell of a virus is made up of many protein molecules, which join to make units called capsomers, and these units together make up the capsid.
• Capsid proteins are always encoded by the virus genome.
• Icosahedral capsids have twenty faces, and are named after the twenty-sided shape called an icosahedron.
• Filamentous capsids are named after their linear, thin, thread-like appearance and may also be called rod-shaped or helical.
• These capsids are kind of a hybrid between the filamentous and icosahedral shapes, consisting of an icosahedral head attached to a filamentous tail.
• Tobacco Mosaic Virus (TMV) was the first virus to be discovered.
• Viruses with envelopes do not provide instructions for the envelope lipids.
• Envelopes contain proteins that are specified by the virus, which often help viral particles bind to host cells.
• All viruses have genetic material (a genome) made of nucleic acid.
• Viruses may use either RNA or DNA: Double-stranded DNA, Double-stranded RNA, Single-stranded DNA, or Single-stranded RNA.
• RNA Viruses: RNA ➤ DNA ➤ integration in host genome ➤ RNA ➤ Protein.
• RNA gets reverse transcribed into DNA that then gets integrated into the host genome.
• Viral infections involve the following steps: Attachment, Entry, Genome replication and gene expression, Assembly, Release.
• Influenza is an enveloped virus with a lipid membrane outer layer that is inserted into glycoproteins HA (hemagglutinin) and NA (neuraminidase), which determine the subtype of influenza virus.
• Influenza has a total of 16 different HA and 9 different NA serotypes or subtypes, which are found in different species and recombine to form novel influenza virus strains.
• Antigenic drift is driven by antibody-mediated selective pressure and a high rate of viral mutations, permitting the virus to escape immunity induced through previous exposure or vaccination, resulting in seasonal epidemics.
• Antigenic shift is a sporadic event and refers to the introduction into human beings of a novel virus strain to which a large proportion of the population does not have immunity, resulting in pandemics.
• The 1918 flu pandemic, known as Spanish flu, was caused by the H1N1 influenza A virus and infected 500 million people, resulting in a death toll of ~50 million, making it one of the deadliest pandemics in human history.
• Human Immunodeficiency Virus (HIV) infects CD4+ T cells of the immune system, causing individuals to become more susceptible to opportunistic infections.
• The acute phase of HIV infection is characterized by a dramatic reduction of CD4+ T cells in the peripheral blood, followed by a rebound after the initial burst of viremia.
• HIV causes progressive loss of CD4+ T cells after several years, leading to immunodeficiency and the development of characteristic infectious that define AIDS.
• Coronaviruses (CoV) are a large family of viruses that cause illness ranging from the common cold to more severe diseases such as Middle East Respiratory Syndrome (MERS-CoV) and Severe Acute Respiratory Syndrome (SARS-CoV).
• Coronaviruses are zoonotic, meaning they are transmitted between animals and people.
• The emergence and rapid spread of COVID-19 signifies a perfect epidemiological storm, with a respiratory pathogen of relatively high virulence from a virus family that jumped species boundaries emerging in a major population centre and travel hub shortly before the biggest travel period of the year: the Chinese Spring Festival.
• Bats are likely the reservoir hosts for SARS-CoV-2, with other mammalian species acting as ‘‘intermediate’’ or ‘‘amplifying’’ hosts, within which SARS-CoV-2 was able to acquire some or all of the mutations needed for efficient human transmission.
• Pangolins are a culinary delicacy in China and are believed to have health benefits.
• Urbanization and deforestation have threatened civets and put them in closer contact with the horseshoe bat which was shown to carry the SARS virus.
• Pangolins are frequently involved in illegal trafficking and their endangered status and presence of a virus related to SARS-CoV-2 suggests related coronaviruses exist in a variety of mammalian species.
• The clinical phenotype of COVID-19 patients in the first and second phase of the epidemic was older, more likely to be male, and likely to have exposure to the seafood market.
• Asymptomatic manifestation of COVID-19 jeopardizes the screening of infected people by temperature measurements or by overt signs and symptoms.
• COVID-19 infection can result in an excessive inflammatory response by the immune system in an attempt to fight the infection.
• Excessive inflammation damages the alveoli, crucial for absorbing oxygen, leading to Acute Respiratory Distress Syndrome (ARDS).