TORONTO -- As the COVID-19 pandemic spreads around the world, so has an image of grey and red spiky fuzzball representing the new coronavirus.

The 3D rendering has become the unmistakable image of SARS-CoV-2, the novel coronavirus that causes COVID-19, as it's been used to illustrate news reports and public health notices around the world.

The now-familiar image of the speckled sphere is a medical illustration and not an actual photograph of the virus, but it still serves an educational purpose.

The 3D image represents what scientists see peering at COVID-19 under a microscope. However, showing COVID-19 in illustration form makes its features much more distinct and helps researchers and the public better understand the virus.

So if you're wondering what each part of the illustration represents, CTVNews.ca breaks it down.

WHAT EACH PART MEANS

A separate version of the illustration released by the Centers for Disease Control and Prevention (CDC) labels the different parts of the coronavirus.

coronavirus illustration with labels

Like other viruses, SARS-CoV-2 is a particle of genetic material wrapped in protein. When viewed close up, the individual COVID-19 appears round with smaller particles attached in clumps. The vibrant colours highlight the difference between the various components of the virus and would not appear when looking at the virus with one’s own eyes.

The grey surface surrounds the nucleus of the virus and is made up of genetic material. Its primary function is to bind the other virus proteins together.

The orange bulbs are membrane proteins or M proteins, and give COVID-19 its structural form. These proteins are what help identify one virus from another.

The yellow bits are envelope proteins or E proteins and help the red spikes latch onto human cells. They are the smallest of the structural proteins, but researchers say they "play an important role either in regulating virus replication -- such as virus entry -- assembly and release."

The red spikes, also called spike proteins or S proteins, are what allow the virus to attack to human cells. These clumps of proteins help the virus enter the body and bind to cells to make copies of itself. The spikes also create a halo, or corona, effect around the nucleus that gives the virus its name.

According to U.S. researchers, the red spikes are "10 to 20 times more likely to bind" to human cells than the spikes from the 2002 SARS coronavirus. This is said to make COVID-19 spread more easily from person-to-person than the earlier virus.

Using an illustration of COVID-19 -- rather than an electron microscope image that can look similar to other respiratory coronaviruses -- shows how artists can help make a seemingly terrifying medical concept seem comprehensible when given a visual form.

coronavirus microscope view

HOW IT WAS MADE

The image was created by medical illustrators Alissa Eckert and Dan Higgins, who were given the assignment by the CDC in mid-January.

Eckert told The New York Times earlier this month that they gathered input from medical experts on what COVID-19 looks like up close and used the Protein Data Bank (PDB) to help create the illustration.

According to a study published in the Biomedical Imaging and Intervention Journal, the Protein Data Bank -- a repository of more than 160,000 molecular structures -- lets scientists and illustrators look up different virus structures and visualize them.

The modelling software is able to create a 3D structure based on previous virus structures and new data submitted.

However, a model from the data bank can be complex and is usually refined before being released to a mass audience.

The model is put through an Autodesk software called 3ds Max, which is used by game developers and animators, to simplify its design. This system is where qualities including appearance and texture can be adjusted until the most effective visual representation of a virus is achieved.

Once the final model is assembled, illustrators then choose the colours and lighting to bring the image together.