The Virus : Infection Dynamics

Transmission: Humans are the rats in this plague. Transmission of COVID-19 is primarily human-human (H2H) with the virus being aspirated by an infected human in various sizes of liquid droplets. Gravity causes the larger, heavier drops (>5um in dia) to fall on nearby surfaces where the virus can be transferred by physical contact and subsequent self-touching (eyes, nose, mouth). The virus can remain active on surfaces anywhere from hours to days depending on the surface material.

Smaller droplets (aersols, <20um) remain suspended in the air and can travel much further (8m+) as in a sneeze or via active ventilation in a conditioned space and remain for up to 16 hrs.. They are more likely to make it past leaks in loose fitting masks and be inhaled deeper into the lungs. Airborne transmission is now understood as the main mode of transmission and a pivotal consideration for any policy on re-opening the economy.

Level of Exposure: The best guess is a few hundred viruses is sufficient to infect a person.

Asymptotic carriers are a major concern as infected carriers without symptoms are less likely to adhere to recommended isolation practices, increasing the risk of spreading the disease. Surprisingly high numbers of asymptotic carriers have been reported in studies ( >80% !! ) which has some upside as it possibly indicates a higher level of immunity than expected, perhaps as the result of T-cells kicking in from a similar previous infection. There is a lot more to learn.

The Virus :

What’s different?

Flu-like viruses including the coronavirus are not completely unknown in humans but the velocity and scope of this pandemic are highlighting key differences from what is known to epidemiologists.

• It is new to humans. The immune system takes time to develop a response. SARS-C0V-2 is different enough that there isn’t an existing “blueprint” to mount a defense.

  • There is some promising news with T-cells, possibly as the result of previous vaccines.

• It is deceptive. It has the ability to block the production of interferons which serve as a warning signal to the immune system. You can be infected and not feel it. The number of asymptotic carriers has been surprisingly high.

• It peaks about a day before you feel sick. A highly contagious person could be spreading the disease without knowing it.

• It does peculiar things experts never would have expected.

  • It causes deadly blood clots and corrupts lung cells into malfunctioning clumps (syncytia).

  • It can kick the immune system into overdrive causing runaway inflammation.

  • It has a strong association with obesity which hasn't been seen with other viral infections.

  • Residual health concerns have been noted for lungs, heart, brain, kidneys, etc.

  • It spreads in hot weather.

So far, the virus doesn’t seem to be playing by the rules when it comes to traditional immunity theory.

• Scientists have discovered patients who had recovered from infection, but mysteriously didn’t develop any antibodies.

• There is growing doubt about how long people who have been infected with SARS-CoV-2 remain immune to the disease.

• There is some evidence to suggest that while antibodies can be detected in patients who have recovered from a severe case of COVID-19 for at least three months, a growing number of studies that show in milder cases the antibodies appear to rapidly decline from around three months after infection.

• Although rare, there is at least one documented case where it might be possible to get it twice.

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“I can promise you that over the next two years, we’ll learn a lot of things that we wish we’d known now that we are going to learn as we move forward.” (Offit, HG 2020)