Part 1: SARS-COV-19 (COVID-19) – Virology

COVID-19:

I bet you think you’ve read everything there is to know about the virus. The amount of information out there regarding COVID-19 is vast; we are here to help you tease out what information is legitimate, valid, and helpful in a sea of articles.

COVID-19, or coronavirus disease 2019, is a disease caused by the coronavirus SARS-2 (SARS-COV-2). This novel zoonotic virus made the leap from an animal (likely a bat) to a human sometime in November 2019 in Wuhan, China

SARS-COV-2 is an RNA virus; once the virus is released into our cells, our own cell machinery begins to copy the viral RNA (instead of our own RNA) and make new viral particles. Eventually the new viral particles are released from our cells, looking for new cells to invade. SARS-COV-2 viral particles look like little balls, with different types of membrane proteins sticking out of its envelope. These membrane proteins play a critical role in the viral replication cycle and are also responsible for the virus’s genus name – coronavirus (corona means “crown” in Latin).

How Does the Virus Replicate in Humans?

First, the SARS-COV-2 virus is very effective at entering host cells. It does this via the spiky envelope protein aptly named “Spike” which binds to the cellular protein ACE2. Second, the SARS-COV-2 virus is pathogenic – this means that it not only can enter the cell, but it can also cause disease. A virus’s ability to cause disease (and the severity of that disease) is often determined by the host’s response: the health status of the individual, genetics, etc. Most COVID-19 disease symptoms are caused by the inflammatory response within the host’s infected tissues. This response largely depends on the person who is infected, their overall health condition, and the circumstances of which they were infected.

The vast variety of human genetics and host response is responsible for the comparably vast disease presentation of SARS-COV-2; some individuals present with mild symptoms, some with severe pneumonia.

What About Different Strains?

Every time the virus copies its genome, mistakes are made. RNA viruses are especially prone to mistakes (1 in every 1000 units of the genome that gets copied) due to the error-prone nature of the enzyme which replicates their genome. These mistakes are called “mutations”; many of these are silent, meaning they have no effect on the way the virus works. Some are not – these mutations can affect the workings of the virus, sometimes, giving the virus an advantage, such as more effective replication in host cells, replication in a wider variety of hosts, etc.

Mutations are notoriously difficult to maintain within a viral genome; most mutations are selected out of the population. Thus, the likelihood of the virus mutating on its own to become more lethal to humans in small. If a treatment or vaccine is developed, the selective pressure on the virus to mutate is slightly higher, meaning the likelihood of the virus evolving a countermeasure to evade this treatment or vaccine is higher.

Anti-viral drug resistance has been shown with other drugs (such as influenza evolving to be resistant to Tamiflu) and immunity to vaccines via changing surface antigens is commonplace; this is the reason we require yearly flu shots.

Why is Hand Washing the Best Thing to do?

Remember the Spike proteins which stick out of the viral envelope? Soap disrupts the envelope, which inactivates the Spike protein. Without this protein, the viral particle cannot enter cells and cause disease. Soap is even more effective the hand sanitizer – washing with soap not only disrupts the viral envelope, but also washes away the disrupted viral particles.

How long do SARS-COV-2 viral particles stick around in the air and on surfaces? Aerosols (droplets from coughs and sneezes) can be present in the air for 3-hours. Viral particles can “survive” on plastic and stainless steel for 48-72 hours (after 72 hours, levels of infectious viral particles are 1000X less) and on paper/cardboard for <24 hours.

Questions about this? Reach out to our team to speak with a professional! Read the next post in this series; Part II – SARS-COV-19 (COVID-19) – Transmission and Disease.