Electron micrograph of COV-2 virus attaching and entering a cell. Note the surface proteins on the virus.

The SARS-COV-2 virus (causing coronavirus disease 2019 (COVID-19) in very small respiratory droplets (smaller than 10-micron diameter) can persist in the air and can travel by local air currents before they drop to the ground. The COV-2 virus is shed by infected person’s respiration by coughing, sneezing and touching nose or mouth and then touching surfaces and can last for days:

• Airborne: up to 3 hrs
• Cardboard: up to 24 hrs
• Plastic and stainless steel: up to 3 days

However, like most biological moieties the virus needs hydration in order to maintain its protein structure for infectivity.

EVAPORATE WATER HYDRATION LAYER:

To understand how to kill the COV-2 virus, we need to know the biochemistry and cell biology underlying the infection mechanism. The outer shell of the virus is made of protein protruding from the bilipid layer of the virus membrane. It is the structure of both these elements that are necessary for viral integrity. A hydration layer made of water molecules are loosely attracted to the protein in an ordered structure (clatherin coat type) through charged (electrostatic) interaction. When this water coat evaporates the protein structure is disrupted, (called desiccation). An everyday example is a tomato that withers and wrinkles over days as the water and other molecules evaporate, causing proteins and other structures to denature. That is why the virus is inactivated more quickly when it is on cardboard compared to stainless steel or plastic surfaces. The cardboard wicks away the water molecules in three dimensions thereby drying out the virus. The stainless steel or plastic only allows for the water to evaporate in a two-dimensional geometry which takes longer. So, what happens to the protruding viral protein? As the water disappears, the protein three-dimensional structure (tertiary  conformation), which is important to the virus bioactivity, changes (it denatures) and no longer can penetrate cells. To penetrate the cells, the virus’ external protruding protein is recognized by surface proteins of cells called receptors, like a lock and key mechanism. So, if the protein structure is disrupted, it cannot fit into the receptors of the cells, therefore is not infectious. Another example is the egg white (ovalbumin), which is a viscous liquid normally, but when boiled, the protein changes it tertiary structure, denatures, and becomes the solid egg white we all recognize.

SOAP:

Washing your hands for 20 seconds with soap and water will destroy the virus. The biochemistry of soap is a bifunctional molecule where ½ is organic loving (oils, grease) with its long chain of carbon atoms and is non-charged and the other ½ is charged (typically phosphate) and loves water. So, the soap latches onto the lipid bilayer of the virus and disrupts its integrity (the ordered “stacking” of the lipids internal to the membrane).  The charged part of the soap is surrounded by charged water molecules, which in turn pull the non-charged part of the soap, now inserted into the membrane, destroying the membrane by opening up the virus, thereby killing it, rendering in non-infectious. The diagram below shows that the lipid bilayer can no longer contain the RNA that renders the virus infectious.

In this diagram, the soap is the blue molecule, with the long hydrocarbon tail inserted into the lipid bilayer of the COV-2 virus, disrupting the virus membrane resulting in loss of infectivity.