We’ve all seen pictures of the SARS-CoV2 coronavirus, but until now most of these have been artists impressions and diagrams. Now new images from the CDC taken from samples from the first American case of COVID-19 show the virus in incredible detail.
The new images from the CDC Public Health Image Library (PHIL) show the SARS-CoV2 virus looking like small pepperoni pizzas (colored blue in the image above). But, these images are hard and labor-intensive to produce and for most people with COVID-19, pictures like this will never be made.
“If you want to see and be able to identify viruses, much less determine any detail on them which helps you categorize them, you have to use an electron microscope,” said Bryan William Jones, PhD, associate professor of ophthalmology and neuroscience at the University of Utah, who has been using electron microscopy for over 20 years.Today In: Healthcare
With some infectious diseases, actually looking down microscopes to identify the type of pathogen is a common way for microbiologists to diagnose patients. However, viruses are simply too small to see using most conventional microscopes, so this technique is used mostly for bacterial and fungal infections.
“There are many kinds of viruses and they all have different sizes. The largest viruses are about 500nm in diameter which means that you could only see them as dots in a light microscope. The smallest are around 20nm in size which means that you could never see them in a light microscope,” said Jones.
At the moment, SARS-CoV2, the coronavirus causing the worldwide pandemic, is detected using a PCR test, which looks for traces of the virus genetic information in samples taken from people with suspected COVID-19. The new images are taken by microscopes which use electrons and magnets to focus and produce images, rather than light and glass lenses found in most conventional microscopes.
So why can’t the coronavirus be tested for using electron microscopes? Firstly, the microscopes are incredibly expensive to buy, around $1 million for a new, top of the range model, so not affordable for many diagnostic labs. They are often large compared to most conventional laboratory microscopes and also require highly-trained, specialist users. It is also unlikely that scientists would be able to tell images of the SARS-CoV2 coronavirus apart from other coronaviruses, such as those which cause some common colds.
So, needless to say the technique is impractical, inaccurate and unnecessary for widespread diagnostic use. However, electron microscopes can help scientists better understand viruses in research settings.
“The virus shape, or morphology is another very important way of categorizing types of viruses, and this is where electron microscopy is important. The scanning electron microscopy images let us see the overall 3D structure of the COVID-19 viruses which include the nucleocapsid protein (N-protein), and a slight fuzz that is the spike protein (explained in this article)on the outside of the coat,” said Jones.
There are two main types of electron microscopes, transmission and scanning. Transmission electron microscopes produce a flat image, and scanning electron microscopes produce more 3D-like pictures. Unlike light microscopes, the images that come from all types of electron microscopes are black and white. The below image has not been artificially colored, any colors are put on afterwards to draw attention to certain aspects of a photo.
“The blue dots in the transmission electron microscope COVID-19 image (title image above) and the orange blobs in the scanning electron microscope COVID-19 image (below, from the NIH), for example, have been artificially colored to more easily show them to viewers who might not be expert virologists who may know precisely what to look for,” said Jones.
The CDC images are not the first electron microscope images of the virus, with these first coming out in February, courtesy of the National Institutes of Health/National Institute of Allergy and Infectious Diseases.