Here’s what COVID-19 actually does to your body: The number of confirmed COVID-19 cases has now surpassed 600,000 globally. Thankfully, the vast majority of these cases are mild. However, there have been almost 30,000 deaths attributed to this novel coronavirus.
The virus, to use its full title, Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), causes respiratory illness. Symptoms range from a mild cough to acute pneumonia. COVID-19 affects the lungs, like the viruses SARS and MERS, but it can also have devastating effects on the rest of the body.
Much remains undiscovered about the virus, but experts are learning about how the virus enters the body, and what happens if you become infected.
To find out more, we spoke to Dr Greg Maguire, Fulbright-Fogarty Fellow at the National Institutes of Health, and author of Thinking and Eating For Two: The Science of Using Systems 1 and 2 Thinking to Nourish Self and Symbionts.
How does coronavirus enter the body?
Coronavirus can enter the body in several ways. In common to other respiratory viruses, the primary manner is through inhalation. If an infected person coughs or sneezes, the virus particles can remain in the air for some time in tiny droplets. When you breathe in through the mouth or nose, the virus enters your body.
Another less common way is through the eyes, nose, or mouth if you touch your face with contaminated hands.
The virus causes harm at the site where it enters the body. For many people, this means a stuffy or runny nose. With luck, your immune system can tackle the virus before it makes its way further into the respiratory system. If not, it passes into the lungs.
How your immune system responds
When any pathogen invades your body, your immune system jumps into action. The coronavirus looks like a sphere covered in spikes. Those spikes are surface proteins, and they are the reason why the virus can successfully invade the cells in your respiratory tract.
The cells in your lungs, arteries, heart, kidneys, and intestines have a protein on their surface called angiotensin-converting enzyme 2 (ACE2). Once the virus binds to these proteins, it uses them as a gateway into your cells.
‘Once the virus enters the body, it enters our cells through a two-step process. In the first stage, the spike proteins on the virus bind to ACE2 receptors located on host cells,’ explains Dr Maguire.
During the second stage of the process, the virus hijacks a special enzyme called a protease that speeds up the breakdown of protein. There are lots of different proteases, but the one that SARS-CoV-2 targets is called TMPRRS2.
Dr Maguire goes on to explain that ‘the spike proteins on the virus must also bind to a protease on the host cells, thought to include the protease TMPRRS2. Once this happens, the protease cleaves the spike protein on the virus in two places, allowing the virus to fuse with the host cell and deposit its RNA into the cells.’ Once it’s inside a cell, it can cause real damage.
RNA is viral genetic material. The virus uses the mechanisms inside your cell to replicate its RNA and make copies of itself. The process destroys cells and creates thousands of new viral particles that infect other cells in the respiratory tract.
Types of immunity
You have three types of immunity called passive, innate, and adaptive. Passive immunity is borrowed from another source, such as breast milk from mothers. It doesn’t play much of a part in immunity from COVID-19 for most of us.
The innate immune system includes skin, mucous membranes, and a generalised, initial immune cell response that your body uses to combat general invaders. It’s not as powerful as adaptive immunity.
Adaptive immunity is like a library of immune cells. As you go through life, you continually encounter pathogens, including viruses, bacteria, fungi, and parasites. These microorganisms can cause disease. Your immune system builds a fighting force of specialised cells called antibodies that remember each pathogen.
Because SARS-CoV-2 is an entirely new or novel virus, your immune system doesn’t recognise it, and you don’t have an adaptive response at first.
