A Simple Tutorial on COVID-19

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March 16, 2020

Viruses unlike bacteria are not self-replicating. They can only replicate inside a host cell in a living organism. The virus uses mechanisms available in the host cell to multiply. 


COVID-19 is a type of virus with an envelope. The virus builds the envelope using proteins and lipids (fats) available in the host cells. The envelope typically exists only when the virus is between host cells, e.g. during transmission in the environment.


An enveloped virus such as COVID-19 has three levels of structure, 

  1. A RNA or DNA (COVID-19 is RNA based),
  2. Surrounded by a protein coating called capsi
  3. Covered by a lipid (I.e. fat)

There are essentially 4 ways to stop a virus prior to infection.

  1. Attack the lipid coating. Using soap or detergent to wash away the virus when it is on a surface (e.g. on hands). Since the virus has an oily coating soap is very effective in dissolving the virus with its molecule (called micelle). Soap itself will dissolve in water and can be washed away. Alcohol is also a good solvent for the virus. Higher temperatures combined with higher humidity in the atmosphere can create enough osmotic pressure to rupture the envelope and make the virus inviable.
  1. Attack the protein coating. The protein coating is a set of complex folded protein structures. The protein can be unfolded if the environment of the virus has a raised temperature, sub-optimal pH, or has ions that can break the bonds within the folded protein. Higher temperature in the atmosphere will make the virus ineffective by destroying the protein coating.
  1. Attack the RNA. This is how most anti-viral medications work. They have enzymes that split the RNA and disable the virus so they can’t replicate. They are similar to how antibiotics work on bacteria. Developing anti-viral medications means finding the right enzymes for each type of virus. There are no general anti-viral medications unlike antibiotics for killing bacteria. Other anti-viral medications work by inhibiting the RNA replication. A new class of drugs are being investigated that inhibit the binding of the virus protein to the host cell receptors (notably ACE2 receptor).
  1. Prevent the virus from invading host cells. This is how our immune system acts against virus invasion. The immune system generates antibodies that recognize  and capture the antigens (in this case the virus) and removes or prevents the virus from invading host cells. Each specific type of virus may require new antibodies. So for some viruses a person may already have working antibodies but for other viruses the immune system must generate new antibodies. Vaccines generally work by pre-pumping the immune system with copies of the virus protein to generate antibodies.