Why Enveloped Viruses Are Susceptible To Disinfectant

Some viruses are surrounded by a lipid membrane known as an envelope.

A virus is an infectious agent like bacteria, worms and fungi, which is composed of proteins and contains only one kind of nucleic acid, either DNA or RNA (2). Viruses do not reproduce by division, like bacteria, yeasts or other cells does, but rather replicate in the living cells that they infect. In some species, they are surrounded by a lipid membrane known as an envelope. For years, biologists had considered viruses as by-products of biological evolution that could have only played a minor role in the history of the living world. However, as a result of multiple advancements in several domains of biology, this has steadily changed (1).

Understanding the origin of viruses has attracted a lot of attention from scholars. As a result, three ideas about the origin of viruses have emerged. The first is the independent entities theory which explains that viruses evolved from a self-replicating material that existed in the prebiotic mRNA world. The second virus hypothesis, known as the reduction/degenerate/regressive evolution theory, claims that viruses evolved when cells of unicellular organisms lost their membranes, cell walls, and other structures, as well as their cytoplasm, leaving only nucleic acid and a few vital proteins to live as parasites in other cells. Last but not least, the escape hypothesis states that viruses evolved from bits of genetic material that fled the cell's control and became parasitic (3).

Viruses are classified into distinct families depending on a set of characteristics. These include the nature of the genome (RNA or DNA), the symmetric form of the capsids, the size of the virion, the site of viral replication within the cell (cytoplasm or nucleus) and the presence of an envelope (2). Viruses can also be divided into non-enveloped and enveloped viruses. Although all viruses must bind to a live host cell to exist, the likelihood of spreading is directly proportional to the viral survival period on the surface, which varies greatly amongst viruses. Most zoonotic viruses, such as human coronaviruses (SARS-CoV2), are enveloped viruses that can stay infectious on surfaces for several days. Most enveloped viruses have a significantly better chance of surviving when they are transmitted through direct contact with surfaces and subsequently propagated by contacting the mucosa of the nose or the conjunctiva of the eye. According to a recent study, the COVID-19 coronavirus may survive the longest on propylene plastic surfaces and stainless-steel surfaces. (4).

The viruses with envelope membranes protect the viral genome. This membrane is made up of lipids (fat) and proteins from host cells as well as viral glycoproteins (sugars combined with proteins). Because these viruses' lipid bilayer envelopes are more susceptible to desiccation, heat, and amphiphiles such as soap and detergents, they are easier to sterilize than non-enveloped viruses. Viruses surrounded with an envelope have particular advantages, and it can be difficult to destroy the virus's genome. The envelope increases the packaging capacity of a virus particle and allows for carrying additional viral proteins. It hides structurally restricted capsid antigens from circulating antibodies, and envelope proteins have a higher structural flexibility than capsid proteins, allowing the virus to exit from its host cell using the cellular machinery for exocytosis, avoiding cell damage and immune responses (5).

The contact time, disinfection agent concentration, and the specific virus involved are the key parameters that influence the efficacy of disinfection agents against viruses, and they can also be influenced by environmental factors. If disinfection requires chemical reactions, the rate of disinfection will be faster at higher temperatures.

Interfering with the envelope of a virus could potentially reduce virus infectivity. During the SARS-CoV2 outbreak, while scientists worked to identify therapeutics and vaccines to protect Mankind from the virus, the World Health Organization (WHO) developed various strategies to combat it. The most effective method of control has been the use of disinfectants containing alcohol, specifically isopropyl alcohol (also known as isopropanol and propan-2-ol) and ethyl alcohol (ethanol).

Enveloped viruses can also be deactivated with a common household chemical, such as soap. One of WHO’s recommended protocols is to wash one's hands with soap under running water. Soap dissolves fat and breaks open the lipid membrane, causing the virus particle to collapse and become non-infectious. Furthermore, soap and detergents are 'surfactants,' which are compounds with a head that is attracted to water (hydrophilic) and a tail that is attracted to fat and grease (hydrophobic). As a result, when amphipathic (having both hydrophilic and hydrophobic parts) soap molecules come into contact with a virus's lipid membrane, the hydrophobic tail sticks to the fatty membrane while the hydrophilic head attracts water, allowing the virus to be lifted off and washed away. As the virus is dislodged, it is surrounded by more soap molecules, which break open the lipid viral membrane and kill it. (6).

SARS-CoV-2 (an enveloped virus) is still in existence, therefore let us all continue to protect ourselves and those around us. As of mid-January 2022, approximately 10 vaccines have received the WHO Emergency Use Listing (a process that determines whether a product can be recommended for use based on all available data on safety and efficacy, as well as its suitability in low and middle-income countries).

Get vaccinated and follow all local vaccination guidance.

Keep a physical distance of at least one meter from others.

Clean your hands frequently with alcohol-based hygienic products and wash your hands with soap under running water.

Remain and stay safe!
The COVID-19 Diary (an initiative by the AAU TV in partnership with the National Research Foundation, South Africa) is inviting you to participate in its 3^rd edition, which is scheduled on 14^th March 2022 at 12:30pm UCT. The theme for this virtual webinar is “Vaccines, Variants and Herd Immunity”. This edition promises to be insightful, transformative and very informative.

Register via the link: https://bit.ly/36pHjSt to participate, and for more information email [email protected] or [email protected].

Author: Isabella Tetteh Ahinakwa (Host, The COVID-19 Diary, a programme run by the Association of African Universities’ TV)