Scaling SARS-CoV-2: Weighing the Viral Load in the World

Have you ever tried to comprehend the sheer number of SARS-CoV-2 viral particles in circulation globally? It's a fascinating—or perhaps even mind-boggling—question. Let's dive into the science and calculations behind this concept.

Understanding the Scale of SARS-CoV-2

Each individual SARS-CoV-2 virion is incredibly small, with a diameter around 100 nanometers (nm). To give you an idea of its size, imagine a garden pea, which is about 10,000 times larger. This tiny size makes it challenging to visualize the cumulative impact of viral particles when they reach astronomical numbers.

The Viral Math: A Simplified Breakdown

Assuming a total of 100 billion viral particles in circulation at any given time, how much do these particles weigh? To address this, let's use some scientific data and perform a little estimation (or SWAG—Scientific Wild Ass Guess).

Typically, an SARS-CoV-2 virion weighs about 1 femtogram (fg), which is equivalent to 1 x 10-15 grams. To put this into perspective, if each virus was like a garden pea, they would only fill less than a cup or two.

The Global Viral Calculation

Considering that an infected person can carry around 1014 to 1015 virions in their body, the weight of viral particles can be estimated for a broader population. For instance, during the first week of an infection, with roughly 4 million people being infected, the total weight of SARS-CoV-2 viral particles in circulation is around 400 kg to 4 tonnes.

However, this is just one scenario. The actual weight can vary significantly depending on the infection rate and the total number of infected individuals. For a more solid estimation, let's consider a few key data points:

Active Cases: Approximately 27,728,270 active cases. Average Person's Weight: About 137 pounds (62 kg). Infected Lungs: If an infected human has 100 million virions in their lungs, they would weigh about 10 nanograms. Global Infections: Assuming 3 million official positive cases, this could represent around 100 million real positive cases, resulting in a total viral load of 1 gram!

The Visual Representation: A Sphere of Viruses

Now, let's take a look at how the physical space these viral particles occupy. If you lined up 100 million virions side by side, the linear length would be 100 nm x 100 million 10,000,000,000 nanometers, or 1 million kilometers. That's the distance from the Earth to the Moon and back—many times!

But if you packed these virions together to form a single sphere, the diameter would be a mere 10 cm. This visualization helps us appreciate the scale of the SARS-CoV-2 in the world, even though the number of particles is astronomical.

These calculations are just speculative and illustrate the complexity and magnitude of the viral load during a pandemic. They serve as both a scientific curiosity and a sobering reminder of the impact of viral transmission on a global scale.